changeset 17945:97634ef9dd1c

8005704: Update ConcurrentHashMap to v8 Reviewed-by: chegar, mduigou
author dl
date Tue, 04 Jun 2013 21:59:23 +0100
parents bbd67fc49daa
children 7791613dcbfd
files jdk/src/share/classes/java/util/concurrent/ConcurrentHashMap.java
diffstat 1 files changed, 5372 insertions(+), 1072 deletions(-) [+]
line wrap: on
line diff
--- a/jdk/src/share/classes/java/util/concurrent/ConcurrentHashMap.java	Tue Jun 04 10:33:13 2013 -0700
+++ b/jdk/src/share/classes/java/util/concurrent/ConcurrentHashMap.java	Tue Jun 04 21:59:23 2013 +0100
@@ -34,14 +34,47 @@
  */
 
 package java.util.concurrent;
-import java.io.ObjectInputStream;
-import java.util.concurrent.locks.*;
-import java.util.*;
 import java.io.Serializable;
+import java.io.ObjectStreamField;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.AbstractMap;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.ConcurrentModificationException;
+import java.util.Enumeration;
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.concurrent.locks.StampedLock;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
+import java.util.function.BinaryOperator;
+import java.util.function.Consumer;
+import java.util.function.DoubleBinaryOperator;
+import java.util.function.Function;
+import java.util.function.IntBinaryOperator;
+import java.util.function.LongBinaryOperator;
+import java.util.function.ToDoubleBiFunction;
+import java.util.function.ToDoubleFunction;
+import java.util.function.ToIntBiFunction;
+import java.util.function.ToIntFunction;
+import java.util.function.ToLongBiFunction;
+import java.util.function.ToLongFunction;
+import java.util.stream.Stream;
 
 /**
  * A hash table supporting full concurrency of retrievals and
- * adjustable expected concurrency for updates. This class obeys the
+ * high expected concurrency for updates. This class obeys the
  * same functional specification as {@link java.util.Hashtable}, and
  * includes versions of methods corresponding to each method of
  * {@code Hashtable}. However, even though all operations are
@@ -51,35 +84,61 @@
  * interoperable with {@code Hashtable} in programs that rely on its
  * thread safety but not on its synchronization details.
  *
- * <p> Retrieval operations (including {@code get}) generally do not
- * block, so may overlap with update operations (including
- * {@code put} and {@code remove}). Retrievals reflect the results
- * of the most recently <em>completed</em> update operations holding
- * upon their onset.  For aggregate operations such as {@code putAll}
- * and {@code clear}, concurrent retrievals may reflect insertion or
- * removal of only some entries.  Similarly, Iterators and
- * Enumerations return elements reflecting the state of the hash table
- * at some point at or since the creation of the iterator/enumeration.
- * They do <em>not</em> throw {@link ConcurrentModificationException}.
- * However, iterators are designed to be used by only one thread at a time.
+ * <p>Retrieval operations (including {@code get}) generally do not
+ * block, so may overlap with update operations (including {@code put}
+ * and {@code remove}). Retrievals reflect the results of the most
+ * recently <em>completed</em> update operations holding upon their
+ * onset. (More formally, an update operation for a given key bears a
+ * <em>happens-before</em> relation with any (non-null) retrieval for
+ * that key reporting the updated value.)  For aggregate operations
+ * such as {@code putAll} and {@code clear}, concurrent retrievals may
+ * reflect insertion or removal of only some entries.  Similarly,
+ * Iterators and Enumerations return elements reflecting the state of
+ * the hash table at some point at or since the creation of the
+ * iterator/enumeration.  They do <em>not</em> throw {@link
+ * ConcurrentModificationException}.  However, iterators are designed
+ * to be used by only one thread at a time.  Bear in mind that the
+ * results of aggregate status methods including {@code size}, {@code
+ * isEmpty}, and {@code containsValue} are typically useful only when
+ * a map is not undergoing concurrent updates in other threads.
+ * Otherwise the results of these methods reflect transient states
+ * that may be adequate for monitoring or estimation purposes, but not
+ * for program control.
  *
- * <p> The allowed concurrency among update operations is guided by
- * the optional {@code concurrencyLevel} constructor argument
- * (default {@code 16}), which is used as a hint for internal sizing.  The
- * table is internally partitioned to try to permit the indicated
- * number of concurrent updates without contention. Because placement
- * in hash tables is essentially random, the actual concurrency will
- * vary.  Ideally, you should choose a value to accommodate as many
- * threads as will ever concurrently modify the table. Using a
- * significantly higher value than you need can waste space and time,
- * and a significantly lower value can lead to thread contention. But
- * overestimates and underestimates within an order of magnitude do
- * not usually have much noticeable impact. A value of one is
- * appropriate when it is known that only one thread will modify and
- * all others will only read. Also, resizing this or any other kind of
- * hash table is a relatively slow operation, so, when possible, it is
- * a good idea to provide estimates of expected table sizes in
- * constructors.
+ * <p>The table is dynamically expanded when there are too many
+ * collisions (i.e., keys that have distinct hash codes but fall into
+ * the same slot modulo the table size), with the expected average
+ * effect of maintaining roughly two bins per mapping (corresponding
+ * to a 0.75 load factor threshold for resizing). There may be much
+ * variance around this average as mappings are added and removed, but
+ * overall, this maintains a commonly accepted time/space tradeoff for
+ * hash tables.  However, resizing this or any other kind of hash
+ * table may be a relatively slow operation. When possible, it is a
+ * good idea to provide a size estimate as an optional {@code
+ * initialCapacity} constructor argument. An additional optional
+ * {@code loadFactor} constructor argument provides a further means of
+ * customizing initial table capacity by specifying the table density
+ * to be used in calculating the amount of space to allocate for the
+ * given number of elements.  Also, for compatibility with previous
+ * versions of this class, constructors may optionally specify an
+ * expected {@code concurrencyLevel} as an additional hint for
+ * internal sizing.  Note that using many keys with exactly the same
+ * {@code hashCode()} is a sure way to slow down performance of any
+ * hash table. To ameliorate impact, when keys are {@link Comparable},
+ * this class may use comparison order among keys to help break ties.
+ *
+ * <p>A {@link Set} projection of a ConcurrentHashMap may be created
+ * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
+ * (using {@link #keySet(Object)} when only keys are of interest, and the
+ * mapped values are (perhaps transiently) not used or all take the
+ * same mapping value.
+ *
+ * <p>A ConcurrentHashMap can be used as scalable frequency map (a
+ * form of histogram or multiset) by using {@link
+ * java.util.concurrent.atomic.LongAdder} values and initializing via
+ * {@link #computeIfAbsent computeIfAbsent}. For example, to add a count
+ * to a {@code ConcurrentHashMap<String,LongAdder> freqs}, you can use
+ * {@code freqs.computeIfAbsent(k -> new LongAdder()).increment();}
  *
  * <p>This class and its views and iterators implement all of the
  * <em>optional</em> methods of the {@link Map} and {@link Iterator}
@@ -88,6 +147,114 @@
  * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class
  * does <em>not</em> allow {@code null} to be used as a key or value.
  *
+ * <p>ConcurrentHashMaps support a set of sequential and parallel bulk
+ * operations that, unlike most {@link Stream} methods, are designed
+ * to be safely, and often sensibly, applied even with maps that are
+ * being concurrently updated by other threads; for example, when
+ * computing a snapshot summary of the values in a shared registry.
+ * There are three kinds of operation, each with four forms, accepting
+ * functions with Keys, Values, Entries, and (Key, Value) arguments
+ * and/or return values. Because the elements of a ConcurrentHashMap
+ * are not ordered in any particular way, and may be processed in
+ * different orders in different parallel executions, the correctness
+ * of supplied functions should not depend on any ordering, or on any
+ * other objects or values that may transiently change while
+ * computation is in progress; and except for forEach actions, should
+ * ideally be side-effect-free. Bulk operations on {@link java.util.Map.Entry}
+ * objects do not support method {@code setValue}.
+ *
+ * <ul>
+ * <li> forEach: Perform a given action on each element.
+ * A variant form applies a given transformation on each element
+ * before performing the action.</li>
+ *
+ * <li> search: Return the first available non-null result of
+ * applying a given function on each element; skipping further
+ * search when a result is found.</li>
+ *
+ * <li> reduce: Accumulate each element.  The supplied reduction
+ * function cannot rely on ordering (more formally, it should be
+ * both associative and commutative).  There are five variants:
+ *
+ * <ul>
+ *
+ * <li> Plain reductions. (There is not a form of this method for
+ * (key, value) function arguments since there is no corresponding
+ * return type.)</li>
+ *
+ * <li> Mapped reductions that accumulate the results of a given
+ * function applied to each element.</li>
+ *
+ * <li> Reductions to scalar doubles, longs, and ints, using a
+ * given basis value.</li>
+ *
+ * </ul>
+ * </li>
+ * </ul>
+ *
+ * <p>These bulk operations accept a {@code parallelismThreshold}
+ * argument. Methods proceed sequentially if the current map size is
+ * estimated to be less than the given threshold. Using a value of
+ * {@code Long.MAX_VALUE} suppresses all parallelism.  Using a value
+ * of {@code 1} results in maximal parallelism by partitioning into
+ * enough subtasks to fully utilize the {@link
+ * ForkJoinPool#commonPool()} that is used for all parallel
+ * computations. Normally, you would initially choose one of these
+ * extreme values, and then measure performance of using in-between
+ * values that trade off overhead versus throughput.
+ *
+ * <p>The concurrency properties of bulk operations follow
+ * from those of ConcurrentHashMap: Any non-null result returned
+ * from {@code get(key)} and related access methods bears a
+ * happens-before relation with the associated insertion or
+ * update.  The result of any bulk operation reflects the
+ * composition of these per-element relations (but is not
+ * necessarily atomic with respect to the map as a whole unless it
+ * is somehow known to be quiescent).  Conversely, because keys
+ * and values in the map are never null, null serves as a reliable
+ * atomic indicator of the current lack of any result.  To
+ * maintain this property, null serves as an implicit basis for
+ * all non-scalar reduction operations. For the double, long, and
+ * int versions, the basis should be one that, when combined with
+ * any other value, returns that other value (more formally, it
+ * should be the identity element for the reduction). Most common
+ * reductions have these properties; for example, computing a sum
+ * with basis 0 or a minimum with basis MAX_VALUE.
+ *
+ * <p>Search and transformation functions provided as arguments
+ * should similarly return null to indicate the lack of any result
+ * (in which case it is not used). In the case of mapped
+ * reductions, this also enables transformations to serve as
+ * filters, returning null (or, in the case of primitive
+ * specializations, the identity basis) if the element should not
+ * be combined. You can create compound transformations and
+ * filterings by composing them yourself under this "null means
+ * there is nothing there now" rule before using them in search or
+ * reduce operations.
+ *
+ * <p>Methods accepting and/or returning Entry arguments maintain
+ * key-value associations. They may be useful for example when
+ * finding the key for the greatest value. Note that "plain" Entry
+ * arguments can be supplied using {@code new
+ * AbstractMap.SimpleEntry(k,v)}.
+ *
+ * <p>Bulk operations may complete abruptly, throwing an
+ * exception encountered in the application of a supplied
+ * function. Bear in mind when handling such exceptions that other
+ * concurrently executing functions could also have thrown
+ * exceptions, or would have done so if the first exception had
+ * not occurred.
+ *
+ * <p>Speedups for parallel compared to sequential forms are common
+ * but not guaranteed.  Parallel operations involving brief functions
+ * on small maps may execute more slowly than sequential forms if the
+ * underlying work to parallelize the computation is more expensive
+ * than the computation itself.  Similarly, parallelization may not
+ * lead to much actual parallelism if all processors are busy
+ * performing unrelated tasks.
+ *
+ * <p>All arguments to all task methods must be non-null.
+ *
  * <p>This class is a member of the
  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
  * Java Collections Framework</a>.
@@ -97,735 +264,2371 @@
  * @param <K> the type of keys maintained by this map
  * @param <V> the type of mapped values
  */
-public class ConcurrentHashMap<K, V> extends AbstractMap<K, V>
-        implements ConcurrentMap<K, V>, Serializable {
+@SuppressWarnings({"unchecked", "rawtypes", "serial"})
+public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
+    implements ConcurrentMap<K,V>, Serializable {
+
     private static final long serialVersionUID = 7249069246763182397L;
 
     /*
-     * The basic strategy is to subdivide the table among Segments,
-     * each of which itself is a concurrently readable hash table.  To
-     * reduce footprint, all but one segments are constructed only
-     * when first needed (see ensureSegment). To maintain visibility
-     * in the presence of lazy construction, accesses to segments as
-     * well as elements of segment's table must use volatile access,
-     * which is done via Unsafe within methods segmentAt etc
-     * below. These provide the functionality of AtomicReferenceArrays
-     * but reduce the levels of indirection. Additionally,
-     * volatile-writes of table elements and entry "next" fields
-     * within locked operations use the cheaper "lazySet" forms of
-     * writes (via putOrderedObject) because these writes are always
-     * followed by lock releases that maintain sequential consistency
-     * of table updates.
+     * Overview:
      *
-     * Historical note: The previous version of this class relied
-     * heavily on "final" fields, which avoided some volatile reads at
-     * the expense of a large initial footprint.  Some remnants of
-     * that design (including forced construction of segment 0) exist
-     * to ensure serialization compatibility.
+     * The primary design goal of this hash table is to maintain
+     * concurrent readability (typically method get(), but also
+     * iterators and related methods) while minimizing update
+     * contention. Secondary goals are to keep space consumption about
+     * the same or better than java.util.HashMap, and to support high
+     * initial insertion rates on an empty table by many threads.
+     *
+     * Each key-value mapping is held in a Node.  Because Node key
+     * fields can contain special values, they are defined using plain
+     * Object types (not type "K"). This leads to a lot of explicit
+     * casting (and the use of class-wide warning suppressions).  It
+     * also allows some of the public methods to be factored into a
+     * smaller number of internal methods (although sadly not so for
+     * the five variants of put-related operations). The
+     * validation-based approach explained below leads to a lot of
+     * code sprawl because retry-control precludes factoring into
+     * smaller methods.
+     *
+     * The table is lazily initialized to a power-of-two size upon the
+     * first insertion.  Each bin in the table normally contains a
+     * list of Nodes (most often, the list has only zero or one Node).
+     * Table accesses require volatile/atomic reads, writes, and
+     * CASes.  Because there is no other way to arrange this without
+     * adding further indirections, we use intrinsics
+     * (sun.misc.Unsafe) operations.
+     *
+     * We use the top (sign) bit of Node hash fields for control
+     * purposes -- it is available anyway because of addressing
+     * constraints.  Nodes with negative hash fields are forwarding
+     * nodes to either TreeBins or resized tables.  The lower 31 bits
+     * of each normal Node's hash field contain a transformation of
+     * the key's hash code.
+     *
+     * Insertion (via put or its variants) of the first node in an
+     * empty bin is performed by just CASing it to the bin.  This is
+     * by far the most common case for put operations under most
+     * key/hash distributions.  Other update operations (insert,
+     * delete, and replace) require locks.  We do not want to waste
+     * the space required to associate a distinct lock object with
+     * each bin, so instead use the first node of a bin list itself as
+     * a lock. Locking support for these locks relies on builtin
+     * "synchronized" monitors.
+     *
+     * Using the first node of a list as a lock does not by itself
+     * suffice though: When a node is locked, any update must first
+     * validate that it is still the first node after locking it, and
+     * retry if not. Because new nodes are always appended to lists,
+     * once a node is first in a bin, it remains first until deleted
+     * or the bin becomes invalidated (upon resizing).
+     *
+     * The main disadvantage of per-bin locks is that other update
+     * operations on other nodes in a bin list protected by the same
+     * lock can stall, for example when user equals() or mapping
+     * functions take a long time.  However, statistically, under
+     * random hash codes, this is not a common problem.  Ideally, the
+     * frequency of nodes in bins follows a Poisson distribution
+     * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
+     * parameter of about 0.5 on average, given the resizing threshold
+     * of 0.75, although with a large variance because of resizing
+     * granularity. Ignoring variance, the expected occurrences of
+     * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The
+     * first values are:
+     *
+     * 0:    0.60653066
+     * 1:    0.30326533
+     * 2:    0.07581633
+     * 3:    0.01263606
+     * 4:    0.00157952
+     * 5:    0.00015795
+     * 6:    0.00001316
+     * 7:    0.00000094
+     * 8:    0.00000006
+     * more: less than 1 in ten million
+     *
+     * Lock contention probability for two threads accessing distinct
+     * elements is roughly 1 / (8 * #elements) under random hashes.
+     *
+     * Actual hash code distributions encountered in practice
+     * sometimes deviate significantly from uniform randomness.  This
+     * includes the case when N > (1<<30), so some keys MUST collide.
+     * Similarly for dumb or hostile usages in which multiple keys are
+     * designed to have identical hash codes. Also, although we guard
+     * against the worst effects of this (see method spread), sets of
+     * hashes may differ only in bits that do not impact their bin
+     * index for a given power-of-two mask.  So we use a secondary
+     * strategy that applies when the number of nodes in a bin exceeds
+     * a threshold, and at least one of the keys implements
+     * Comparable.  These TreeBins use a balanced tree to hold nodes
+     * (a specialized form of red-black trees), bounding search time
+     * to O(log N).  Each search step in a TreeBin is at least twice as
+     * slow as in a regular list, but given that N cannot exceed
+     * (1<<64) (before running out of addresses) this bounds search
+     * steps, lock hold times, etc, to reasonable constants (roughly
+     * 100 nodes inspected per operation worst case) so long as keys
+     * are Comparable (which is very common -- String, Long, etc).
+     * TreeBin nodes (TreeNodes) also maintain the same "next"
+     * traversal pointers as regular nodes, so can be traversed in
+     * iterators in the same way.
+     *
+     * The table is resized when occupancy exceeds a percentage
+     * threshold (nominally, 0.75, but see below).  Any thread
+     * noticing an overfull bin may assist in resizing after the
+     * initiating thread allocates and sets up the replacement
+     * array. However, rather than stalling, these other threads may
+     * proceed with insertions etc.  The use of TreeBins shields us
+     * from the worst case effects of overfilling while resizes are in
+     * progress.  Resizing proceeds by transferring bins, one by one,
+     * from the table to the next table. To enable concurrency, the
+     * next table must be (incrementally) prefilled with place-holders
+     * serving as reverse forwarders to the old table.  Because we are
+     * using power-of-two expansion, the elements from each bin must
+     * either stay at same index, or move with a power of two
+     * offset. We eliminate unnecessary node creation by catching
+     * cases where old nodes can be reused because their next fields
+     * won't change.  On average, only about one-sixth of them need
+     * cloning when a table doubles. The nodes they replace will be
+     * garbage collectable as soon as they are no longer referenced by
+     * any reader thread that may be in the midst of concurrently
+     * traversing table.  Upon transfer, the old table bin contains
+     * only a special forwarding node (with hash field "MOVED") that
+     * contains the next table as its key. On encountering a
+     * forwarding node, access and update operations restart, using
+     * the new table.
+     *
+     * Each bin transfer requires its bin lock, which can stall
+     * waiting for locks while resizing. However, because other
+     * threads can join in and help resize rather than contend for
+     * locks, average aggregate waits become shorter as resizing
+     * progresses.  The transfer operation must also ensure that all
+     * accessible bins in both the old and new table are usable by any
+     * traversal.  This is arranged by proceeding from the last bin
+     * (table.length - 1) up towards the first.  Upon seeing a
+     * forwarding node, traversals (see class Traverser) arrange to
+     * move to the new table without revisiting nodes.  However, to
+     * ensure that no intervening nodes are skipped, bin splitting can
+     * only begin after the associated reverse-forwarders are in
+     * place.
+     *
+     * The traversal scheme also applies to partial traversals of
+     * ranges of bins (via an alternate Traverser constructor)
+     * to support partitioned aggregate operations.  Also, read-only
+     * operations give up if ever forwarded to a null table, which
+     * provides support for shutdown-style clearing, which is also not
+     * currently implemented.
+     *
+     * Lazy table initialization minimizes footprint until first use,
+     * and also avoids resizings when the first operation is from a
+     * putAll, constructor with map argument, or deserialization.
+     * These cases attempt to override the initial capacity settings,
+     * but harmlessly fail to take effect in cases of races.
+     *
+     * The element count is maintained using a specialization of
+     * LongAdder. We need to incorporate a specialization rather than
+     * just use a LongAdder in order to access implicit
+     * contention-sensing that leads to creation of multiple
+     * Cells.  The counter mechanics avoid contention on
+     * updates but can encounter cache thrashing if read too
+     * frequently during concurrent access. To avoid reading so often,
+     * resizing under contention is attempted only upon adding to a
+     * bin already holding two or more nodes. Under uniform hash
+     * distributions, the probability of this occurring at threshold
+     * is around 13%, meaning that only about 1 in 8 puts check
+     * threshold (and after resizing, many fewer do so). The bulk
+     * putAll operation further reduces contention by only committing
+     * count updates upon these size checks.
+     *
+     * Maintaining API and serialization compatibility with previous
+     * versions of this class introduces several oddities. Mainly: We
+     * leave untouched but unused constructor arguments refering to
+     * concurrencyLevel. We accept a loadFactor constructor argument,
+     * but apply it only to initial table capacity (which is the only
+     * time that we can guarantee to honor it.) We also declare an
+     * unused "Segment" class that is instantiated in minimal form
+     * only when serializing.
      */
 
     /* ---------------- Constants -------------- */
 
     /**
-     * The default initial capacity for this table,
-     * used when not otherwise specified in a constructor.
+     * The largest possible table capacity.  This value must be
+     * exactly 1<<30 to stay within Java array allocation and indexing
+     * bounds for power of two table sizes, and is further required
+     * because the top two bits of 32bit hash fields are used for
+     * control purposes.
      */
-    static final int DEFAULT_INITIAL_CAPACITY = 16;
+    private static final int MAXIMUM_CAPACITY = 1 << 30;
 
     /**
-     * The default load factor for this table, used when not
-     * otherwise specified in a constructor.
+     * The default initial table capacity.  Must be a power of 2
+     * (i.e., at least 1) and at most MAXIMUM_CAPACITY.
      */
-    static final float DEFAULT_LOAD_FACTOR = 0.75f;
+    private static final int DEFAULT_CAPACITY = 16;
 
     /**
-     * The default concurrency level for this table, used when not
-     * otherwise specified in a constructor.
+     * The largest possible (non-power of two) array size.
+     * Needed by toArray and related methods.
      */
-    static final int DEFAULT_CONCURRENCY_LEVEL = 16;
+    static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
 
     /**
-     * The maximum capacity, used if a higher value is implicitly
-     * specified by either of the constructors with arguments.  MUST
-     * be a power of two <= 1<<30 to ensure that entries are indexable
-     * using ints.
+     * The default concurrency level for this table. Unused but
+     * defined for compatibility with previous versions of this class.
      */
-    static final int MAXIMUM_CAPACITY = 1 << 30;
+    private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
 
     /**
-     * The minimum capacity for per-segment tables.  Must be a power
-     * of two, at least two to avoid immediate resizing on next use
-     * after lazy construction.
+     * The load factor for this table. Overrides of this value in
+     * constructors affect only the initial table capacity.  The
+     * actual floating point value isn't normally used -- it is
+     * simpler to use expressions such as {@code n - (n >>> 2)} for
+     * the associated resizing threshold.
      */
-    static final int MIN_SEGMENT_TABLE_CAPACITY = 2;
+    private static final float LOAD_FACTOR = 0.75f;
 
     /**
-     * The maximum number of segments to allow; used to bound
-     * constructor arguments. Must be power of two less than 1 << 24.
+     * The bin count threshold for using a tree rather than list for a
+     * bin.  The value reflects the approximate break-even point for
+     * using tree-based operations.
      */
-    static final int MAX_SEGMENTS = 1 << 16; // slightly conservative
+    private static final int TREE_THRESHOLD = 8;
 
     /**
-     * Number of unsynchronized retries in size and containsValue
-     * methods before resorting to locking. This is used to avoid
-     * unbounded retries if tables undergo continuous modification
-     * which would make it impossible to obtain an accurate result.
+     * Minimum number of rebinnings per transfer step. Ranges are
+     * subdivided to allow multiple resizer threads.  This value
+     * serves as a lower bound to avoid resizers encountering
+     * excessive memory contention.  The value should be at least
+     * DEFAULT_CAPACITY.
      */
-    static final int RETRIES_BEFORE_LOCK = 2;
+    private static final int MIN_TRANSFER_STRIDE = 16;
+
+    /*
+     * Encodings for Node hash fields. See above for explanation.
+     */
+    static final int MOVED     = 0x80000000; // hash field for forwarding nodes
+    static final int HASH_BITS = 0x7fffffff; // usable bits of normal node hash
+
+    /** Number of CPUS, to place bounds on some sizings */
+    static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+    /** For serialization compatibility. */
+    private static final ObjectStreamField[] serialPersistentFields = {
+        new ObjectStreamField("segments", Segment[].class),
+        new ObjectStreamField("segmentMask", Integer.TYPE),
+        new ObjectStreamField("segmentShift", Integer.TYPE)
+    };
+
+    /**
+     * A padded cell for distributing counts.  Adapted from LongAdder
+     * and Striped64.  See their internal docs for explanation.
+     */
+    @sun.misc.Contended static final class Cell {
+        volatile long value;
+        Cell(long x) { value = x; }
+    }
 
     /* ---------------- Fields -------------- */
 
     /**
-     * A randomizing value associated with this instance that is applied to
-     * hash code of keys to make hash collisions harder to find.
+     * The array of bins. Lazily initialized upon first insertion.
+     * Size is always a power of two. Accessed directly by iterators.
      */
-   private transient final int hashSeed = sun.misc.Hashing.randomHashSeed(this);
+    transient volatile Node<K,V>[] table;
 
     /**
-     * Mask value for indexing into segments. The upper bits of a
-     * key's hash code are used to choose the segment.
+     * The next table to use; non-null only while resizing.
      */
-    final int segmentMask;
+    private transient volatile Node<K,V>[] nextTable;
 
     /**
-     * Shift value for indexing within segments.
+     * Base counter value, used mainly when there is no contention,
+     * but also as a fallback during table initialization
+     * races. Updated via CAS.
      */
-    final int segmentShift;
+    private transient volatile long baseCount;
 
     /**
-     * The segments, each of which is a specialized hash table.
+     * Table initialization and resizing control.  When negative, the
+     * table is being initialized or resized: -1 for initialization,
+     * else -(1 + the number of active resizing threads).  Otherwise,
+     * when table is null, holds the initial table size to use upon
+     * creation, or 0 for default. After initialization, holds the
+     * next element count value upon which to resize the table.
      */
-    final Segment<K,V>[] segments;
-
-    transient Set<K> keySet;
-    transient Set<Map.Entry<K,V>> entrySet;
-    transient Collection<V> values;
+    private transient volatile int sizeCtl;
 
     /**
-     * ConcurrentHashMap list entry. Note that this is never exported
-     * out as a user-visible Map.Entry.
+     * The next table index (plus one) to split while resizing.
      */
-    static final class HashEntry<K,V> {
+    private transient volatile int transferIndex;
+
+    /**
+     * The least available table index to split while resizing.
+     */
+    private transient volatile int transferOrigin;
+
+    /**
+     * Spinlock (locked via CAS) used when resizing and/or creating Cells.
+     */
+    private transient volatile int cellsBusy;
+
+    /**
+     * Table of counter cells. When non-null, size is a power of 2.
+     */
+    private transient volatile Cell[] counterCells;
+
+    // views
+    private transient KeySetView<K,V> keySet;
+    private transient ValuesView<K,V> values;
+    private transient EntrySetView<K,V> entrySet;
+
+    /* ---------------- Table element access -------------- */
+
+    /*
+     * Volatile access methods are used for table elements as well as
+     * elements of in-progress next table while resizing.  Uses are
+     * null checked by callers, and implicitly bounds-checked, relying
+     * on the invariants that tab arrays have non-zero size, and all
+     * indices are masked with (tab.length - 1) which is never
+     * negative and always less than length. Note that, to be correct
+     * wrt arbitrary concurrency errors by users, bounds checks must
+     * operate on local variables, which accounts for some odd-looking
+     * inline assignments below.
+     */
+
+    static final <K,V> Node<K,V> tabAt(Node<K,V>[] tab, int i) {
+        return (Node<K,V>)U.getObjectVolatile(tab, ((long)i << ASHIFT) + ABASE);
+    }
+
+    static final <K,V> boolean casTabAt(Node<K,V>[] tab, int i,
+                                        Node<K,V> c, Node<K,V> v) {
+        return U.compareAndSwapObject(tab, ((long)i << ASHIFT) + ABASE, c, v);
+    }
+
+    static final <K,V> void setTabAt(Node<K,V>[] tab, int i, Node<K,V> v) {
+        U.putObjectVolatile(tab, ((long)i << ASHIFT) + ABASE, v);
+    }
+
+    /* ---------------- Nodes -------------- */
+
+    /**
+     * Key-value entry.  This class is never exported out as a
+     * user-mutable Map.Entry (i.e., one supporting setValue; see
+     * MapEntry below), but can be used for read-only traversals used
+     * in bulk tasks.  Nodes with a hash field of MOVED are special,
+     * and do not contain user keys or values (and are never
+     * exported).  Otherwise, keys and vals are never null.
+     */
+    static class Node<K,V> implements Map.Entry<K,V> {
         final int hash;
-        final K key;
-        volatile V value;
-        volatile HashEntry<K,V> next;
-
-        HashEntry(int hash, K key, V value, HashEntry<K,V> next) {
+        final Object key;
+        volatile V val;
+        Node<K,V> next;
+
+        Node(int hash, Object key, V val, Node<K,V> next) {
             this.hash = hash;
             this.key = key;
-            this.value = value;
+            this.val = val;
             this.next = next;
         }
 
+        public final K getKey()       { return (K)key; }
+        public final V getValue()     { return val; }
+        public final int hashCode()   { return key.hashCode() ^ val.hashCode(); }
+        public final String toString(){ return key + "=" + val; }
+        public final V setValue(V value) {
+            throw new UnsupportedOperationException();
+        }
+
+        public final boolean equals(Object o) {
+            Object k, v, u; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    (k == key || k.equals(key)) &&
+                    (v == (u = val) || v.equals(u)));
+        }
+    }
+
+    /**
+     * Exported Entry for EntryIterator
+     */
+    static final class MapEntry<K,V> implements Map.Entry<K,V> {
+        final K key; // non-null
+        V val;       // non-null
+        final ConcurrentHashMap<K,V> map;
+        MapEntry(K key, V val, ConcurrentHashMap<K,V> map) {
+            this.key = key;
+            this.val = val;
+            this.map = map;
+        }
+        public K getKey()        { return key; }
+        public V getValue()      { return val; }
+        public int hashCode()    { return key.hashCode() ^ val.hashCode(); }
+        public String toString() { return key + "=" + val; }
+
+        public boolean equals(Object o) {
+            Object k, v; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    (k == key || k.equals(key)) &&
+                    (v == val || v.equals(val)));
+        }
+
         /**
-         * Sets next field with volatile write semantics.  (See above
-         * about use of putOrderedObject.)
+         * Sets our entry's value and writes through to the map. The
+         * value to return is somewhat arbitrary here. Since we do not
+         * necessarily track asynchronous changes, the most recent
+         * "previous" value could be different from what we return (or
+         * could even have been removed, in which case the put will
+         * re-establish). We do not and cannot guarantee more.
          */
-        final void setNext(HashEntry<K,V> n) {
-            UNSAFE.putOrderedObject(this, nextOffset, n);
+        public V setValue(V value) {
+            if (value == null) throw new NullPointerException();
+            V v = val;
+            val = value;
+            map.put(key, value);
+            return v;
         }
-
-        // Unsafe mechanics
-        static final sun.misc.Unsafe UNSAFE;
-        static final long nextOffset;
-        static {
-            try {
-                UNSAFE = sun.misc.Unsafe.getUnsafe();
-                Class<?> k = HashEntry.class;
-                nextOffset = UNSAFE.objectFieldOffset
-                    (k.getDeclaredField("next"));
-            } catch (Exception e) {
-                throw new Error(e);
+    }
+
+
+    /* ---------------- TreeBins -------------- */
+
+    /**
+     * Nodes for use in TreeBins
+     */
+    static final class TreeNode<K,V> extends Node<K,V> {
+        TreeNode<K,V> parent;  // red-black tree links
+        TreeNode<K,V> left;
+        TreeNode<K,V> right;
+        TreeNode<K,V> prev;    // needed to unlink next upon deletion
+        boolean red;
+
+        TreeNode(int hash, Object key, V val, Node<K,V> next,
+                 TreeNode<K,V> parent) {
+            super(hash, key, val, next);
+            this.parent = parent;
+        }
+    }
+
+    /**
+     * Returns a Class for the given type of the form "class C
+     * implements Comparable<C>", if one exists, else null.  See below
+     * for explanation.
+     */
+    static Class<?> comparableClassFor(Class<?> c) {
+        Class<?> s, cmpc; Type[] ts, as; Type t; ParameterizedType p;
+        if (c == String.class) // bypass checks
+            return c;
+        if (c != null && (cmpc = Comparable.class).isAssignableFrom(c)) {
+            while (cmpc.isAssignableFrom(s = c.getSuperclass()))
+                c = s; // find topmost comparable class
+            if ((ts = c.getGenericInterfaces()) != null) {
+                for (int i = 0; i < ts.length; ++i) {
+                    if (((t = ts[i]) instanceof ParameterizedType) &&
+                        ((p = (ParameterizedType)t).getRawType() == cmpc) &&
+                        (as = p.getActualTypeArguments()) != null &&
+                        as.length == 1 && as[0] == c) // type arg is c
+                        return c;
+                }
             }
         }
+        return null;
     }
 
     /**
-     * Gets the ith element of given table (if nonnull) with volatile
-     * read semantics. Note: This is manually integrated into a few
-     * performance-sensitive methods to reduce call overhead.
+     * A specialized form of red-black tree for use in bins
+     * whose size exceeds a threshold.
+     *
+     * TreeBins use a special form of comparison for search and
+     * related operations (which is the main reason we cannot use
+     * existing collections such as TreeMaps). TreeBins contain
+     * Comparable elements, but may contain others, as well as
+     * elements that are Comparable but not necessarily Comparable
+     * for the same T, so we cannot invoke compareTo among them. To
+     * handle this, the tree is ordered primarily by hash value, then
+     * by Comparable.compareTo order if applicable.  On lookup at a
+     * node, if elements are not comparable or compare as 0 then both
+     * left and right children may need to be searched in the case of
+     * tied hash values. (This corresponds to the full list search
+     * that would be necessary if all elements were non-Comparable and
+     * had tied hashes.)  The red-black balancing code is updated from
+     * pre-jdk-collections
+     * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)
+     * based in turn on Cormen, Leiserson, and Rivest "Introduction to
+     * Algorithms" (CLR).
+     *
+     * TreeBins also maintain a separate locking discipline than
+     * regular bins. Because they are forwarded via special MOVED
+     * nodes at bin heads (which can never change once established),
+     * we cannot use those nodes as locks. Instead, TreeBin extends
+     * StampedLock to support a form of read-write lock. For update
+     * operations and table validation, the exclusive form of lock
+     * behaves in the same way as bin-head locks. However, lookups use
+     * shared read-lock mechanics to allow multiple readers in the
+     * absence of writers.  Additionally, these lookups do not ever
+     * block: While the lock is not available, they proceed along the
+     * slow traversal path (via next-pointers) until the lock becomes
+     * available or the list is exhausted, whichever comes
+     * first. These cases are not fast, but maximize aggregate
+     * expected throughput.
      */
-    @SuppressWarnings("unchecked")
-    static final <K,V> HashEntry<K,V> entryAt(HashEntry<K,V>[] tab, int i) {
-        return (tab == null) ? null :
-            (HashEntry<K,V>) UNSAFE.getObjectVolatile
-            (tab, ((long)i << TSHIFT) + TBASE);
-    }
-
-    /**
-     * Sets the ith element of given table, with volatile write
-     * semantics. (See above about use of putOrderedObject.)
-     */
-    static final <K,V> void setEntryAt(HashEntry<K,V>[] tab, int i,
-                                       HashEntry<K,V> e) {
-        UNSAFE.putOrderedObject(tab, ((long)i << TSHIFT) + TBASE, e);
-    }
-
-    /**
-     * Applies a supplemental hash function to a given hashCode, which
-     * defends against poor quality hash functions.  This is critical
-     * because ConcurrentHashMap uses power-of-two length hash tables,
-     * that otherwise encounter collisions for hashCodes that do not
-     * differ in lower or upper bits.
-     */
-    private int hash(Object k) {
-        if (k instanceof String) {
-            return ((String) k).hash32();
+    static final class TreeBin<K,V> extends StampedLock {
+        private static final long serialVersionUID = 2249069246763182397L;
+        transient TreeNode<K,V> root;  // root of tree
+        transient TreeNode<K,V> first; // head of next-pointer list
+
+        /** From CLR */
+        private void rotateLeft(TreeNode<K,V> p) {
+            if (p != null) {
+                TreeNode<K,V> r = p.right, pp, rl;
+                if ((rl = p.right = r.left) != null)
+                    rl.parent = p;
+                if ((pp = r.parent = p.parent) == null)
+                    root = r;
+                else if (pp.left == p)
+                    pp.left = r;
+                else
+                    pp.right = r;
+                r.left = p;
+                p.parent = r;
+            }
         }
 
-        int h = hashSeed ^ k.hashCode();
-
-        // Spread bits to regularize both segment and index locations,
-        // using variant of single-word Wang/Jenkins hash.
-        h += (h <<  15) ^ 0xffffcd7d;
-        h ^= (h >>> 10);
-        h += (h <<   3);
-        h ^= (h >>>  6);
-        h += (h <<   2) + (h << 14);
-        return h ^ (h >>> 16);
-    }
-
-    /**
-     * Segments are specialized versions of hash tables.  This
-     * subclasses from ReentrantLock opportunistically, just to
-     * simplify some locking and avoid separate construction.
-     */
-    static final class Segment<K,V> extends ReentrantLock implements Serializable {
-        /*
-         * Segments maintain a table of entry lists that are always
-         * kept in a consistent state, so can be read (via volatile
-         * reads of segments and tables) without locking.  This
-         * requires replicating nodes when necessary during table
-         * resizing, so the old lists can be traversed by readers
-         * still using old version of table.
-         *
-         * This class defines only mutative methods requiring locking.
-         * Except as noted, the methods of this class perform the
-         * per-segment versions of ConcurrentHashMap methods.  (Other
-         * methods are integrated directly into ConcurrentHashMap
-         * methods.) These mutative methods use a form of controlled
-         * spinning on contention via methods scanAndLock and
-         * scanAndLockForPut. These intersperse tryLocks with
-         * traversals to locate nodes.  The main benefit is to absorb
-         * cache misses (which are very common for hash tables) while
-         * obtaining locks so that traversal is faster once
-         * acquired. We do not actually use the found nodes since they
-         * must be re-acquired under lock anyway to ensure sequential
-         * consistency of updates (and in any case may be undetectably
-         * stale), but they will normally be much faster to re-locate.
-         * Also, scanAndLockForPut speculatively creates a fresh node
-         * to use in put if no node is found.
+        /** From CLR */
+        private void rotateRight(TreeNode<K,V> p) {
+            if (p != null) {
+                TreeNode<K,V> l = p.left, pp, lr;
+                if ((lr = p.left = l.right) != null)
+                    lr.parent = p;
+                if ((pp = l.parent = p.parent) == null)
+                    root = l;
+                else if (pp.right == p)
+                    pp.right = l;
+                else
+                    pp.left = l;
+                l.right = p;
+                p.parent = l;
+            }
+        }
+
+        /**
+         * Returns the TreeNode (or null if not found) for the given key
+         * starting at given root.
          */
-
-        private static final long serialVersionUID = 2249069246763182397L;
+        final TreeNode<K,V> getTreeNode(int h, Object k, TreeNode<K,V> p,
+                                        Class<?> cc) {
+            while (p != null) {
+                int dir, ph; Object pk; Class<?> pc;
+                if ((ph = p.hash) != h)
+                    dir = (h < ph) ? -1 : 1;
+                else if ((pk = p.key) == k || k.equals(pk))
+                    return p;
+                else if (cc == null || pk == null ||
+                         ((pc = pk.getClass()) != cc &&
+                          comparableClassFor(pc) != cc) ||
+                         (dir = ((Comparable<Object>)k).compareTo(pk)) == 0) {
+                    TreeNode<K,V> r, pr; // check both sides
+                    if ((pr = p.right) != null &&
+                        (r = getTreeNode(h, k, pr, cc)) != null)
+                        return r;
+                    else // continue left
+                        dir = -1;
+                }
+                p = (dir > 0) ? p.right : p.left;
+            }
+            return null;
+        }
 
         /**
-         * The maximum number of times to tryLock in a prescan before
-         * possibly blocking on acquire in preparation for a locked
-         * segment operation. On multiprocessors, using a bounded
-         * number of retries maintains cache acquired while locating
-         * nodes.
+         * Wrapper for getTreeNode used by CHM.get. Tries to obtain
+         * read-lock to call getTreeNode, but during failure to get
+         * lock, searches along next links.
          */
-        static final int MAX_SCAN_RETRIES =
-            Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
+        final V getValue(int h, Object k) {
+            Class<?> cc = comparableClassFor(k.getClass());
+            Node<K,V> r = null;
+            for (Node<K,V> e = first; e != null; e = e.next) {
+                long s;
+                if ((s = tryReadLock()) != 0L) {
+                    try {
+                        r = getTreeNode(h, k, root, cc);
+                    } finally {
+                        unlockRead(s);
+                    }
+                    break;
+                }
+                else if (e.hash == h && k.equals(e.key)) {
+                    r = e;
+                    break;
+                }
+            }
+            return r == null ? null : r.val;
+        }
 
         /**
-         * The per-segment table. Elements are accessed via
-         * entryAt/setEntryAt providing volatile semantics.
+         * Finds or adds a node.
+         * @return null if added
          */
-        transient volatile HashEntry<K,V>[] table;
-
-        /**
-         * The number of elements. Accessed only either within locks
-         * or among other volatile reads that maintain visibility.
-         */
-        transient int count;
-
-        /**
-         * The total number of mutative operations in this segment.
-         * Even though this may overflows 32 bits, it provides
-         * sufficient accuracy for stability checks in CHM isEmpty()
-         * and size() methods.  Accessed only either within locks or
-         * among other volatile reads that maintain visibility.
-         */
-        transient int modCount;
-
-        /**
-         * The table is rehashed when its size exceeds this threshold.
-         * (The value of this field is always {@code (int)(capacity *
-         * loadFactor)}.)
-         */
-        transient int threshold;
-
-        /**
-         * The load factor for the hash table.  Even though this value
-         * is same for all segments, it is replicated to avoid needing
-         * links to outer object.
-         * @serial
-         */
-        final float loadFactor;
-
-        Segment(float lf, int threshold, HashEntry<K,V>[] tab) {
-            this.loadFactor = lf;
-            this.threshold = threshold;
-            this.table = tab;
-        }
-
-        final V put(K key, int hash, V value, boolean onlyIfAbsent) {
-            HashEntry<K,V> node = tryLock() ? null :
-                scanAndLockForPut(key, hash, value);
-            V oldValue;
-            try {
-                HashEntry<K,V>[] tab = table;
-                int index = (tab.length - 1) & hash;
-                HashEntry<K,V> first = entryAt(tab, index);
-                for (HashEntry<K,V> e = first;;) {
-                    if (e != null) {
-                        K k;
-                        if ((k = e.key) == key ||
-                            (e.hash == hash && key.equals(k))) {
-                            oldValue = e.value;
-                            if (!onlyIfAbsent) {
-                                e.value = value;
-                                ++modCount;
+        final TreeNode<K,V> putTreeNode(int h, Object k, V v) {
+            Class<?> cc = comparableClassFor(k.getClass());
+            TreeNode<K,V> pp = root, p = null;
+            int dir = 0;
+            while (pp != null) { // find existing node or leaf to insert at
+                int ph; Object pk; Class<?> pc;
+                p = pp;
+                if ((ph = p.hash) != h)
+                    dir = (h < ph) ? -1 : 1;
+                else if ((pk = p.key) == k || k.equals(pk))
+                    return p;
+                else if (cc == null || pk == null ||
+                         ((pc = pk.getClass()) != cc &&
+                          comparableClassFor(pc) != cc) ||
+                         (dir = ((Comparable<Object>)k).compareTo(pk)) == 0) {
+                    TreeNode<K,V> r, pr;
+                    if ((pr = p.right) != null &&
+                        (r = getTreeNode(h, k, pr, cc)) != null)
+                        return r;
+                    else // continue left
+                        dir = -1;
+                }
+                pp = (dir > 0) ? p.right : p.left;
+            }
+
+            TreeNode<K,V> f = first;
+            TreeNode<K,V> x = first = new TreeNode<K,V>(h, k, v, f, p);
+            if (p == null)
+                root = x;
+            else { // attach and rebalance; adapted from CLR
+                if (f != null)
+                    f.prev = x;
+                if (dir <= 0)
+                    p.left = x;
+                else
+                    p.right = x;
+                x.red = true;
+                for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {
+                    if ((xp = x.parent) == null) {
+                        (root = x).red = false;
+                        break;
+                    }
+                    else if (!xp.red || (xpp = xp.parent) == null) {
+                        TreeNode<K,V> r = root;
+                        if (r != null && r.red)
+                            r.red = false;
+                        break;
+                    }
+                    else if ((xppl = xpp.left) == xp) {
+                        if ((xppr = xpp.right) != null && xppr.red) {
+                            xppr.red = false;
+                            xp.red = false;
+                            xpp.red = true;
+                            x = xpp;
+                        }
+                        else {
+                            if (x == xp.right) {
+                                rotateLeft(x = xp);
+                                xpp = (xp = x.parent) == null ? null : xp.parent;
                             }
-                            break;
+                            if (xp != null) {
+                                xp.red = false;
+                                if (xpp != null) {
+                                    xpp.red = true;
+                                    rotateRight(xpp);
+                                }
+                            }
                         }
-                        e = e.next;
                     }
                     else {
-                        if (node != null)
-                            node.setNext(first);
-                        else
-                            node = new HashEntry<K,V>(hash, key, value, first);
-                        int c = count + 1;
-                        if (c > threshold && tab.length < MAXIMUM_CAPACITY)
-                            rehash(node);
-                        else
-                            setEntryAt(tab, index, node);
-                        ++modCount;
-                        count = c;
-                        oldValue = null;
-                        break;
-                    }
-                }
-            } finally {
-                unlock();
-            }
-            return oldValue;
-        }
-
-        /**
-         * Doubles size of table and repacks entries, also adding the
-         * given node to new table
-         */
-        @SuppressWarnings("unchecked")
-        private void rehash(HashEntry<K,V> node) {
-            /*
-             * Reclassify nodes in each list to new table.  Because we
-             * are using power-of-two expansion, the elements from
-             * each bin must either stay at same index, or move with a
-             * power of two offset. We eliminate unnecessary node
-             * creation by catching cases where old nodes can be
-             * reused because their next fields won't change.
-             * Statistically, at the default threshold, only about
-             * one-sixth of them need cloning when a table
-             * doubles. The nodes they replace will be garbage
-             * collectable as soon as they are no longer referenced by
-             * any reader thread that may be in the midst of
-             * concurrently traversing table. Entry accesses use plain
-             * array indexing because they are followed by volatile
-             * table write.
-             */
-            HashEntry<K,V>[] oldTable = table;
-            int oldCapacity = oldTable.length;
-            int newCapacity = oldCapacity << 1;
-            threshold = (int)(newCapacity * loadFactor);
-            HashEntry<K,V>[] newTable =
-                (HashEntry<K,V>[]) new HashEntry<?,?>[newCapacity];
-            int sizeMask = newCapacity - 1;
-            for (int i = 0; i < oldCapacity ; i++) {
-                HashEntry<K,V> e = oldTable[i];
-                if (e != null) {
-                    HashEntry<K,V> next = e.next;
-                    int idx = e.hash & sizeMask;
-                    if (next == null)   //  Single node on list
-                        newTable[idx] = e;
-                    else { // Reuse consecutive sequence at same slot
-                        HashEntry<K,V> lastRun = e;
-                        int lastIdx = idx;
-                        for (HashEntry<K,V> last = next;
-                             last != null;
-                             last = last.next) {
-                            int k = last.hash & sizeMask;
-                            if (k != lastIdx) {
-                                lastIdx = k;
-                                lastRun = last;
+                        if (xppl != null && xppl.red) {
+                            xppl.red = false;
+                            xp.red = false;
+                            xpp.red = true;
+                            x = xpp;
+                        }
+                        else {
+                            if (x == xp.left) {
+                                rotateRight(x = xp);
+                                xpp = (xp = x.parent) == null ? null : xp.parent;
                             }
-                        }
-                        newTable[lastIdx] = lastRun;
-                        // Clone remaining nodes
-                        for (HashEntry<K,V> p = e; p != lastRun; p = p.next) {
-                            V v = p.value;
-                            int h = p.hash;
-                            int k = h & sizeMask;
-                            HashEntry<K,V> n = newTable[k];
-                            newTable[k] = new HashEntry<K,V>(h, p.key, v, n);
+                            if (xp != null) {
+                                xp.red = false;
+                                if (xpp != null) {
+                                    xpp.red = true;
+                                    rotateLeft(xpp);
+                                }
+                            }
                         }
                     }
                 }
             }
-            int nodeIndex = node.hash & sizeMask; // add the new node
-            node.setNext(newTable[nodeIndex]);
-            newTable[nodeIndex] = node;
-            table = newTable;
+            assert checkInvariants();
+            return null;
         }
 
         /**
-         * Scans for a node containing given key while trying to
-         * acquire lock, creating and returning one if not found. Upon
-         * return, guarantees that lock is held. UNlike in most
-         * methods, calls to method equals are not screened: Since
-         * traversal speed doesn't matter, we might as well help warm
-         * up the associated code and accesses as well.
-         *
-         * @return a new node if key not found, else null
+         * Removes the given node, that must be present before this
+         * call.  This is messier than typical red-black deletion code
+         * because we cannot swap the contents of an interior node
+         * with a leaf successor that is pinned by "next" pointers
+         * that are accessible independently of lock. So instead we
+         * swap the tree linkages.
          */
-        private HashEntry<K,V> scanAndLockForPut(K key, int hash, V value) {
-            HashEntry<K,V> first = entryForHash(this, hash);
-            HashEntry<K,V> e = first;
-            HashEntry<K,V> node = null;
-            int retries = -1; // negative while locating node
-            while (!tryLock()) {
-                HashEntry<K,V> f; // to recheck first below
-                if (retries < 0) {
-                    if (e == null) {
-                        if (node == null) // speculatively create node
-                            node = new HashEntry<K,V>(hash, key, value, null);
-                        retries = 0;
+        final void deleteTreeNode(TreeNode<K,V> p) {
+            TreeNode<K,V> next = (TreeNode<K,V>)p.next;
+            TreeNode<K,V> pred = p.prev;  // unlink traversal pointers
+            if (pred == null)
+                first = next;
+            else
+                pred.next = next;
+            if (next != null)
+                next.prev = pred;
+            else if (pred == null) {
+                root = null;
+                return;
+            }
+            TreeNode<K,V> replacement;
+            TreeNode<K,V> pl = p.left;
+            TreeNode<K,V> pr = p.right;
+            if (pl != null && pr != null) {
+                TreeNode<K,V> s = pr, sl;
+                while ((sl = s.left) != null) // find successor
+                    s = sl;
+                boolean c = s.red; s.red = p.red; p.red = c; // swap colors
+                TreeNode<K,V> sr = s.right;
+                TreeNode<K,V> pp = p.parent;
+                if (s == pr) { // p was s's direct parent
+                    p.parent = s;
+                    s.right = p;
+                }
+                else {
+                    TreeNode<K,V> sp = s.parent;
+                    if ((p.parent = sp) != null) {
+                        if (s == sp.left)
+                            sp.left = p;
+                        else
+                            sp.right = p;
                     }
-                    else if (key.equals(e.key))
-                        retries = 0;
-                    else
-                        e = e.next;
+                    if ((s.right = pr) != null)
+                        pr.parent = s;
                 }
-                else if (++retries > MAX_SCAN_RETRIES) {
-                    lock();
+                p.left = null;
+                if ((p.right = sr) != null)
+                    sr.parent = p;
+                if ((s.left = pl) != null)
+                    pl.parent = s;
+                if ((s.parent = pp) == null)
+                    root = s;
+                else if (p == pp.left)
+                    pp.left = s;
+                else
+                    pp.right = s;
+                if (sr != null)
+                    replacement = sr;
+                else
+                    replacement = p;
+            }
+            else if (pl != null)
+                replacement = pl;
+            else if (pr != null)
+                replacement = pr;
+            else
+                replacement = p;
+            if (replacement != p) {
+                TreeNode<K,V> pp = replacement.parent = p.parent;
+                if (pp == null)
+                    root = replacement;
+                else if (p == pp.left)
+                    pp.left = replacement;
+                else
+                    pp.right = replacement;
+                p.left = p.right = p.parent = null;
+            }
+            if (!p.red) { // rebalance, from CLR
+                for (TreeNode<K,V> x = replacement; x != null; ) {
+                    TreeNode<K,V> xp, xpl, xpr;
+                    if (x.red || (xp = x.parent) == null) {
+                        x.red = false;
+                        break;
+                    }
+                    else if ((xpl = xp.left) == x) {
+                        if ((xpr = xp.right) != null && xpr.red) {
+                            xpr.red = false;
+                            xp.red = true;
+                            rotateLeft(xp);
+                            xpr = (xp = x.parent) == null ? null : xp.right;
+                        }
+                        if (xpr == null)
+                            x = xp;
+                        else {
+                            TreeNode<K,V> sl = xpr.left, sr = xpr.right;
+                            if ((sr == null || !sr.red) &&
+                                (sl == null || !sl.red)) {
+                                xpr.red = true;
+                                x = xp;
+                            }
+                            else {
+                                if (sr == null || !sr.red) {
+                                    if (sl != null)
+                                        sl.red = false;
+                                    xpr.red = true;
+                                    rotateRight(xpr);
+                                    xpr = (xp = x.parent) == null ?
+                                        null : xp.right;
+                                }
+                                if (xpr != null) {
+                                    xpr.red = (xp == null) ? false : xp.red;
+                                    if ((sr = xpr.right) != null)
+                                        sr.red = false;
+                                }
+                                if (xp != null) {
+                                    xp.red = false;
+                                    rotateLeft(xp);
+                                }
+                                x = root;
+                            }
+                        }
+                    }
+                    else { // symmetric
+                        if (xpl != null && xpl.red) {
+                            xpl.red = false;
+                            xp.red = true;
+                            rotateRight(xp);
+                            xpl = (xp = x.parent) == null ? null : xp.left;
+                        }
+                        if (xpl == null)
+                            x = xp;
+                        else {
+                            TreeNode<K,V> sl = xpl.left, sr = xpl.right;
+                            if ((sl == null || !sl.red) &&
+                                (sr == null || !sr.red)) {
+                                xpl.red = true;
+                                x = xp;
+                            }
+                            else {
+                                if (sl == null || !sl.red) {
+                                    if (sr != null)
+                                        sr.red = false;
+                                    xpl.red = true;
+                                    rotateLeft(xpl);
+                                    xpl = (xp = x.parent) == null ?
+                                        null : xp.left;
+                                }
+                                if (xpl != null) {
+                                    xpl.red = (xp == null) ? false : xp.red;
+                                    if ((sl = xpl.left) != null)
+                                        sl.red = false;
+                                }
+                                if (xp != null) {
+                                    xp.red = false;
+                                    rotateRight(xp);
+                                }
+                                x = root;
+                            }
+                        }
+                    }
+                }
+            }
+            if (p == replacement) {  // detach pointers
+                TreeNode<K,V> pp;
+                if ((pp = p.parent) != null) {
+                    if (p == pp.left)
+                        pp.left = null;
+                    else if (p == pp.right)
+                        pp.right = null;
+                    p.parent = null;
+                }
+            }
+            assert checkInvariants();
+        }
+
+        /**
+         * Checks linkage and balance invariants at root
+         */
+        final boolean checkInvariants() {
+            TreeNode<K,V> r = root;
+            if (r == null)
+                return (first == null);
+            else
+                return (first != null) && checkTreeNode(r);
+        }
+
+        /**
+         * Recursive invariant check
+         */
+        final boolean checkTreeNode(TreeNode<K,V> t) {
+            TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
+                tb = t.prev, tn = (TreeNode<K,V>)t.next;
+            if (tb != null && tb.next != t)
+                return false;
+            if (tn != null && tn.prev != t)
+                return false;
+            if (tp != null && t != tp.left && t != tp.right)
+                return false;
+            if (tl != null && (tl.parent != t || tl.hash > t.hash))
+                return false;
+            if (tr != null && (tr.parent != t || tr.hash < t.hash))
+                return false;
+            if (t.red && tl != null && tl.red && tr != null && tr.red)
+                return false;
+            if (tl != null && !checkTreeNode(tl))
+                return false;
+            if (tr != null && !checkTreeNode(tr))
+                return false;
+            return true;
+        }
+    }
+
+    /* ---------------- Collision reduction methods -------------- */
+
+    /**
+     * Spreads higher bits to lower, and also forces top bit to 0.
+     * Because the table uses power-of-two masking, sets of hashes
+     * that vary only in bits above the current mask will always
+     * collide. (Among known examples are sets of Float keys holding
+     * consecutive whole numbers in small tables.)  To counter this,
+     * we apply a transform that spreads the impact of higher bits
+     * downward. There is a tradeoff between speed, utility, and
+     * quality of bit-spreading. Because many common sets of hashes
+     * are already reasonably distributed across bits (so don't benefit
+     * from spreading), and because we use trees to handle large sets
+     * of collisions in bins, we don't need excessively high quality.
+     */
+    private static final int spread(int h) {
+        h ^= (h >>> 18) ^ (h >>> 12);
+        return (h ^ (h >>> 10)) & HASH_BITS;
+    }
+
+    /**
+     * Replaces a list bin with a tree bin if key is comparable.  Call
+     * only when locked.
+     */
+    private final void replaceWithTreeBin(Node<K,V>[] tab, int index, Object key) {
+        if (tab != null && comparableClassFor(key.getClass()) != null) {
+            TreeBin<K,V> t = new TreeBin<K,V>();
+            for (Node<K,V> e = tabAt(tab, index); e != null; e = e.next)
+                t.putTreeNode(e.hash, e.key, e.val);
+            setTabAt(tab, index, new Node<K,V>(MOVED, t, null, null));
+        }
+    }
+
+    /* ---------------- Internal access and update methods -------------- */
+
+    /** Implementation for get and containsKey */
+    private final V internalGet(Object k) {
+        int h = spread(k.hashCode());
+        V v = null;
+        Node<K,V>[] tab; Node<K,V> e;
+        if ((tab = table) != null &&
+            (e = tabAt(tab, (tab.length - 1) & h)) != null) {
+            for (;;) {
+                int eh; Object ek;
+                if ((eh = e.hash) < 0) {
+                    if ((ek = e.key) instanceof TreeBin) { // search TreeBin
+                        v = ((TreeBin<K,V>)ek).getValue(h, k);
+                        break;
+                    }
+                    else if (!(ek instanceof Node[]) ||    // try new table
+                             (e = tabAt(tab = (Node<K,V>[])ek,
+                                        (tab.length - 1) & h)) == null)
+                        break;
+                }
+                else if (eh == h && ((ek = e.key) == k || k.equals(ek))) {
+                    v = e.val;
                     break;
                 }
-                else if ((retries & 1) == 0 &&
-                         (f = entryForHash(this, hash)) != first) {
-                    e = first = f; // re-traverse if entry changed
-                    retries = -1;
+                else if ((e = e.next) == null)
+                    break;
+            }
+        }
+        return v;
+    }
+
+    /**
+     * Implementation for the four public remove/replace methods:
+     * Replaces node value with v, conditional upon match of cv if
+     * non-null.  If resulting value is null, delete.
+     */
+    private final V internalReplace(Object k, V v, Object cv) {
+        int h = spread(k.hashCode());
+        V oldVal = null;
+        for (Node<K,V>[] tab = table;;) {
+            Node<K,V> f; int i, fh; Object fk;
+            if (tab == null ||
+                (f = tabAt(tab, i = (tab.length - 1) & h)) == null)
+                break;
+            else if ((fh = f.hash) < 0) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                    long stamp = t.writeLock();
+                    boolean validated = false;
+                    boolean deleted = false;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            validated = true;
+                            Class<?> cc = comparableClassFor(k.getClass());
+                            TreeNode<K,V> p = t.getTreeNode(h, k, t.root, cc);
+                            if (p != null) {
+                                V pv = p.val;
+                                if (cv == null || cv == pv || cv.equals(pv)) {
+                                    oldVal = pv;
+                                    if (v != null)
+                                        p.val = v;
+                                    else {
+                                        deleted = true;
+                                        t.deleteTreeNode(p);
+                                    }
+                                }
+                            }
+                        }
+                    } finally {
+                        t.unlockWrite(stamp);
+                    }
+                    if (validated) {
+                        if (deleted)
+                            addCount(-1L, -1);
+                        break;
+                    }
                 }
+                else
+                    tab = (Node<K,V>[])fk;
             }
-            return node;
-        }
-
-        /**
-         * Scans for a node containing the given key while trying to
-         * acquire lock for a remove or replace operation. Upon
-         * return, guarantees that lock is held.  Note that we must
-         * lock even if the key is not found, to ensure sequential
-         * consistency of updates.
-         */
-        private void scanAndLock(Object key, int hash) {
-            // similar to but simpler than scanAndLockForPut
-            HashEntry<K,V> first = entryForHash(this, hash);
-            HashEntry<K,V> e = first;
-            int retries = -1;
-            while (!tryLock()) {
-                HashEntry<K,V> f;
-                if (retries < 0) {
-                    if (e == null || key.equals(e.key))
-                        retries = 0;
-                    else
-                        e = e.next;
+            else {
+                boolean validated = false;
+                boolean deleted = false;
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        validated = true;
+                        for (Node<K,V> e = f, pred = null;;) {
+                            Object ek;
+                            if (e.hash == h &&
+                                ((ek = e.key) == k || k.equals(ek))) {
+                                V ev = e.val;
+                                if (cv == null || cv == ev || cv.equals(ev)) {
+                                    oldVal = ev;
+                                    if (v != null)
+                                        e.val = v;
+                                    else {
+                                        deleted = true;
+                                        Node<K,V> en = e.next;
+                                        if (pred != null)
+                                            pred.next = en;
+                                        else
+                                            setTabAt(tab, i, en);
+                                    }
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null)
+                                break;
+                        }
+                    }
                 }
-                else if (++retries > MAX_SCAN_RETRIES) {
-                    lock();
+                if (validated) {
+                    if (deleted)
+                        addCount(-1L, -1);
                     break;
                 }
-                else if ((retries & 1) == 0 &&
-                         (f = entryForHash(this, hash)) != first) {
-                    e = first = f;
-                    retries = -1;
-                }
             }
         }
-
-        /**
-         * Remove; match on key only if value null, else match both.
-         */
-        final V remove(Object key, int hash, Object value) {
-            if (!tryLock())
-                scanAndLock(key, hash);
-            V oldValue = null;
-            try {
-                HashEntry<K,V>[] tab = table;
-                int index = (tab.length - 1) & hash;
-                HashEntry<K,V> e = entryAt(tab, index);
-                HashEntry<K,V> pred = null;
-                while (e != null) {
-                    K k;
-                    HashEntry<K,V> next = e.next;
-                    if ((k = e.key) == key ||
-                        (e.hash == hash && key.equals(k))) {
-                        V v = e.value;
-                        if (value == null || value == v || value.equals(v)) {
-                            if (pred == null)
-                                setEntryAt(tab, index, next);
-                            else
-                                pred.setNext(next);
-                            ++modCount;
-                            --count;
-                            oldValue = v;
+        return oldVal;
+    }
+
+    /*
+     * Internal versions of insertion methods
+     * All have the same basic structure as the first (internalPut):
+     *  1. If table uninitialized, create
+     *  2. If bin empty, try to CAS new node
+     *  3. If bin stale, use new table
+     *  4. if bin converted to TreeBin, validate and relay to TreeBin methods
+     *  5. Lock and validate; if valid, scan and add or update
+     *
+     * The putAll method differs mainly in attempting to pre-allocate
+     * enough table space, and also more lazily performs count updates
+     * and checks.
+     *
+     * Most of the function-accepting methods can't be factored nicely
+     * because they require different functional forms, so instead
+     * sprawl out similar mechanics.
+     */
+
+    /** Implementation for put and putIfAbsent */
+    private final V internalPut(K k, V v, boolean onlyIfAbsent) {
+        if (k == null || v == null) throw new NullPointerException();
+        int h = spread(k.hashCode());
+        int len = 0;
+        for (Node<K,V>[] tab = table;;) {
+            int i, fh; Node<K,V> f; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node<K,V>(h, k, v, null)))
+                    break;                   // no lock when adding to empty bin
+            }
+            else if ((fh = f.hash) < 0) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                    long stamp = t.writeLock();
+                    V oldVal = null;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            len = 2;
+                            TreeNode<K,V> p = t.putTreeNode(h, k, v);
+                            if (p != null) {
+                                oldVal = p.val;
+                                if (!onlyIfAbsent)
+                                    p.val = v;
+                            }
                         }
-                        break;
+                    } finally {
+                        t.unlockWrite(stamp);
                     }
-                    pred = e;
-                    e = next;
-                }
-            } finally {
-                unlock();
-            }
-            return oldValue;
-        }
-
-        final boolean replace(K key, int hash, V oldValue, V newValue) {
-            if (!tryLock())
-                scanAndLock(key, hash);
-            boolean replaced = false;
-            try {
-                HashEntry<K,V> e;
-                for (e = entryForHash(this, hash); e != null; e = e.next) {
-                    K k;
-                    if ((k = e.key) == key ||
-                        (e.hash == hash && key.equals(k))) {
-                        if (oldValue.equals(e.value)) {
-                            e.value = newValue;
-                            ++modCount;
-                            replaced = true;
-                        }
+                    if (len != 0) {
+                        if (oldVal != null)
+                            return oldVal;
                         break;
                     }
                 }
-            } finally {
-                unlock();
+                else
+                    tab = (Node<K,V>[])fk;
             }
-            return replaced;
+            else {
+                V oldVal = null;
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        len = 1;
+                        for (Node<K,V> e = f;; ++len) {
+                            Object ek;
+                            if (e.hash == h &&
+                                ((ek = e.key) == k || k.equals(ek))) {
+                                oldVal = e.val;
+                                if (!onlyIfAbsent)
+                                    e.val = v;
+                                break;
+                            }
+                            Node<K,V> last = e;
+                            if ((e = e.next) == null) {
+                                last.next = new Node<K,V>(h, k, v, null);
+                                if (len > TREE_THRESHOLD)
+                                    replaceWithTreeBin(tab, i, k);
+                                break;
+                            }
+                        }
+                    }
+                }
+                if (len != 0) {
+                    if (oldVal != null)
+                        return oldVal;
+                    break;
+                }
+            }
         }
-
-        final V replace(K key, int hash, V value) {
-            if (!tryLock())
-                scanAndLock(key, hash);
-            V oldValue = null;
-            try {
-                HashEntry<K,V> e;
-                for (e = entryForHash(this, hash); e != null; e = e.next) {
-                    K k;
-                    if ((k = e.key) == key ||
-                        (e.hash == hash && key.equals(k))) {
-                        oldValue = e.value;
-                        e.value = value;
-                        ++modCount;
+        addCount(1L, len);
+        return null;
+    }
+
+    /** Implementation for computeIfAbsent */
+    private final V internalComputeIfAbsent(K k, Function<? super K, ? extends V> mf) {
+        if (k == null || mf == null)
+            throw new NullPointerException();
+        int h = spread(k.hashCode());
+        V val = null;
+        int len = 0;
+        for (Node<K,V>[] tab = table;;) {
+            Node<K,V> f; int i; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                Node<K,V> node = new Node<K,V>(h, k, null, null);
+                synchronized (node) {
+                    if (casTabAt(tab, i, null, node)) {
+                        len = 1;
+                        try {
+                            if ((val = mf.apply(k)) != null)
+                                node.val = val;
+                        } finally {
+                            if (val == null)
+                                setTabAt(tab, i, null);
+                        }
+                    }
+                }
+                if (len != 0)
+                    break;
+            }
+            else if (f.hash < 0) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                    long stamp = t.writeLock();
+                    boolean added = false;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            len = 2;
+                            Class<?> cc = comparableClassFor(k.getClass());
+                            TreeNode<K,V> p = t.getTreeNode(h, k, t.root, cc);
+                            if (p != null)
+                                val = p.val;
+                            else if ((val = mf.apply(k)) != null) {
+                                added = true;
+                                t.putTreeNode(h, k, val);
+                            }
+                        }
+                    } finally {
+                        t.unlockWrite(stamp);
+                    }
+                    if (len != 0) {
+                        if (!added)
+                            return val;
                         break;
                     }
                 }
-            } finally {
-                unlock();
+                else
+                    tab = (Node<K,V>[])fk;
             }
-            return oldValue;
+            else {
+                boolean added = false;
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        len = 1;
+                        for (Node<K,V> e = f;; ++len) {
+                            Object ek; V ev;
+                            if (e.hash == h &&
+                                ((ek = e.key) == k || k.equals(ek))) {
+                                val = e.val;
+                                break;
+                            }
+                            Node<K,V> last = e;
+                            if ((e = e.next) == null) {
+                                if ((val = mf.apply(k)) != null) {
+                                    added = true;
+                                    last.next = new Node<K,V>(h, k, val, null);
+                                    if (len > TREE_THRESHOLD)
+                                        replaceWithTreeBin(tab, i, k);
+                                }
+                                break;
+                            }
+                        }
+                    }
+                }
+                if (len != 0) {
+                    if (!added)
+                        return val;
+                    break;
+                }
+            }
         }
-
-        final void clear() {
-            lock();
-            try {
-                HashEntry<K,V>[] tab = table;
-                for (int i = 0; i < tab.length ; i++)
-                    setEntryAt(tab, i, null);
-                ++modCount;
-                count = 0;
-            } finally {
-                unlock();
+        if (val != null)
+            addCount(1L, len);
+        return val;
+    }
+
+    /** Implementation for compute */
+    private final V internalCompute(K k, boolean onlyIfPresent,
+                                    BiFunction<? super K, ? super V, ? extends V> mf) {
+        if (k == null || mf == null)
+            throw new NullPointerException();
+        int h = spread(k.hashCode());
+        V val = null;
+        int delta = 0;
+        int len = 0;
+        for (Node<K,V>[] tab = table;;) {
+            Node<K,V> f; int i, fh; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (onlyIfPresent)
+                    break;
+                Node<K,V> node = new Node<K,V>(h, k, null, null);
+                synchronized (node) {
+                    if (casTabAt(tab, i, null, node)) {
+                        try {
+                            len = 1;
+                            if ((val = mf.apply(k, null)) != null) {
+                                node.val = val;
+                                delta = 1;
+                            }
+                        } finally {
+                            if (delta == 0)
+                                setTabAt(tab, i, null);
+                        }
+                    }
+                }
+                if (len != 0)
+                    break;
+            }
+            else if ((fh = f.hash) < 0) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                    long stamp = t.writeLock();
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            len = 2;
+                            Class<?> cc = comparableClassFor(k.getClass());
+                            TreeNode<K,V> p = t.getTreeNode(h, k, t.root, cc);
+                            if (p != null || !onlyIfPresent) {
+                                V pv = (p == null) ? null : p.val;
+                                if ((val = mf.apply(k, pv)) != null) {
+                                    if (p != null)
+                                        p.val = val;
+                                    else {
+                                        delta = 1;
+                                        t.putTreeNode(h, k, val);
+                                    }
+                                }
+                                else if (p != null) {
+                                    delta = -1;
+                                    t.deleteTreeNode(p);
+                                }
+                            }
+                        }
+                    } finally {
+                        t.unlockWrite(stamp);
+                    }
+                    if (len != 0)
+                        break;
+                }
+                else
+                    tab = (Node<K,V>[])fk;
+            }
+            else {
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        len = 1;
+                        for (Node<K,V> e = f, pred = null;; ++len) {
+                            Object ek;
+                            if (e.hash == h &&
+                                ((ek = e.key) == k || k.equals(ek))) {
+                                val = mf.apply(k, e.val);
+                                if (val != null)
+                                    e.val = val;
+                                else {
+                                    delta = -1;
+                                    Node<K,V> en = e.next;
+                                    if (pred != null)
+                                        pred.next = en;
+                                    else
+                                        setTabAt(tab, i, en);
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null) {
+                                if (!onlyIfPresent &&
+                                    (val = mf.apply(k, null)) != null) {
+                                    pred.next = new Node<K,V>(h, k, val, null);
+                                    delta = 1;
+                                    if (len > TREE_THRESHOLD)
+                                        replaceWithTreeBin(tab, i, k);
+                                }
+                                break;
+                            }
+                        }
+                    }
+                }
+                if (len != 0)
+                    break;
+            }
+        }
+        if (delta != 0)
+            addCount((long)delta, len);
+        return val;
+    }
+
+    /** Implementation for merge */
+    private final V internalMerge(K k, V v,
+                                  BiFunction<? super V, ? super V, ? extends V> mf) {
+        if (k == null || v == null || mf == null)
+            throw new NullPointerException();
+        int h = spread(k.hashCode());
+        V val = null;
+        int delta = 0;
+        int len = 0;
+        for (Node<K,V>[] tab = table;;) {
+            int i; Node<K,V> f; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node<K,V>(h, k, v, null))) {
+                    delta = 1;
+                    val = v;
+                    break;
+                }
+            }
+            else if (f.hash < 0) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                    long stamp = t.writeLock();
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            len = 2;
+                            Class<?> cc = comparableClassFor(k.getClass());
+                            TreeNode<K,V> p = t.getTreeNode(h, k, t.root, cc);
+                            val = (p == null) ? v : mf.apply(p.val, v);
+                            if (val != null) {
+                                if (p != null)
+                                    p.val = val;
+                                else {
+                                    delta = 1;
+                                    t.putTreeNode(h, k, val);
+                                }
+                            }
+                            else if (p != null) {
+                                delta = -1;
+                                t.deleteTreeNode(p);
+                            }
+                        }
+                    } finally {
+                        t.unlockWrite(stamp);
+                    }
+                    if (len != 0)
+                        break;
+                }
+                else
+                    tab = (Node<K,V>[])fk;
+            }
+            else {
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        len = 1;
+                        for (Node<K,V> e = f, pred = null;; ++len) {
+                            Object ek;
+                            if (e.hash == h &&
+                                ((ek = e.key) == k || k.equals(ek))) {
+                                val = mf.apply(e.val, v);
+                                if (val != null)
+                                    e.val = val;
+                                else {
+                                    delta = -1;
+                                    Node<K,V> en = e.next;
+                                    if (pred != null)
+                                        pred.next = en;
+                                    else
+                                        setTabAt(tab, i, en);
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null) {
+                                delta = 1;
+                                val = v;
+                                pred.next = new Node<K,V>(h, k, val, null);
+                                if (len > TREE_THRESHOLD)
+                                    replaceWithTreeBin(tab, i, k);
+                                break;
+                            }
+                        }
+                    }
+                }
+                if (len != 0)
+                    break;
+            }
+        }
+        if (delta != 0)
+            addCount((long)delta, len);
+        return val;
+    }
+
+    /** Implementation for putAll */
+    private final void internalPutAll(Map<? extends K, ? extends V> m) {
+        tryPresize(m.size());
+        long delta = 0L;     // number of uncommitted additions
+        boolean npe = false; // to throw exception on exit for nulls
+        try {                // to clean up counts on other exceptions
+            for (Map.Entry<?, ? extends V> entry : m.entrySet()) {
+                Object k; V v;
+                if (entry == null || (k = entry.getKey()) == null ||
+                    (v = entry.getValue()) == null) {
+                    npe = true;
+                    break;
+                }
+                int h = spread(k.hashCode());
+                for (Node<K,V>[] tab = table;;) {
+                    int i; Node<K,V> f; int fh; Object fk;
+                    if (tab == null)
+                        tab = initTable();
+                    else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null){
+                        if (casTabAt(tab, i, null, new Node<K,V>(h, k, v, null))) {
+                            ++delta;
+                            break;
+                        }
+                    }
+                    else if ((fh = f.hash) < 0) {
+                        if ((fk = f.key) instanceof TreeBin) {
+                            TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                            long stamp = t.writeLock();
+                            boolean validated = false;
+                            try {
+                                if (tabAt(tab, i) == f) {
+                                    validated = true;
+                                    Class<?> cc = comparableClassFor(k.getClass());
+                                    TreeNode<K,V> p = t.getTreeNode(h, k,
+                                                                    t.root, cc);
+                                    if (p != null)
+                                        p.val = v;
+                                    else {
+                                        ++delta;
+                                        t.putTreeNode(h, k, v);
+                                    }
+                                }
+                            } finally {
+                                t.unlockWrite(stamp);
+                            }
+                            if (validated)
+                                break;
+                        }
+                        else
+                            tab = (Node<K,V>[])fk;
+                    }
+                    else {
+                        int len = 0;
+                        synchronized (f) {
+                            if (tabAt(tab, i) == f) {
+                                len = 1;
+                                for (Node<K,V> e = f;; ++len) {
+                                    Object ek;
+                                    if (e.hash == h &&
+                                        ((ek = e.key) == k || k.equals(ek))) {
+                                        e.val = v;
+                                        break;
+                                    }
+                                    Node<K,V> last = e;
+                                    if ((e = e.next) == null) {
+                                        ++delta;
+                                        last.next = new Node<K,V>(h, k, v, null);
+                                        if (len > TREE_THRESHOLD)
+                                            replaceWithTreeBin(tab, i, k);
+                                        break;
+                                    }
+                                }
+                            }
+                        }
+                        if (len != 0) {
+                            if (len > 1) {
+                                addCount(delta, len);
+                                delta = 0L;
+                            }
+                            break;
+                        }
+                    }
+                }
+            }
+        } finally {
+            if (delta != 0L)
+                addCount(delta, 2);
+        }
+        if (npe)
+            throw new NullPointerException();
+    }
+
+    /**
+     * Implementation for clear. Steps through each bin, removing all
+     * nodes.
+     */
+    private final void internalClear() {
+        long delta = 0L; // negative number of deletions
+        int i = 0;
+        Node<K,V>[] tab = table;
+        while (tab != null && i < tab.length) {
+            Node<K,V> f = tabAt(tab, i);
+            if (f == null)
+                ++i;
+            else if (f.hash < 0) {
+                Object fk;
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                    long stamp = t.writeLock();
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            for (Node<K,V> p = t.first; p != null; p = p.next)
+                                --delta;
+                            t.first = null;
+                            t.root = null;
+                            ++i;
+                        }
+                    } finally {
+                        t.unlockWrite(stamp);
+                    }
+                }
+                else
+                    tab = (Node<K,V>[])fk;
+            }
+            else {
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        for (Node<K,V> e = f; e != null; e = e.next)
+                            --delta;
+                        setTabAt(tab, i, null);
+                        ++i;
+                    }
+                }
+            }
+        }
+        if (delta != 0L)
+            addCount(delta, -1);
+    }
+
+    /* ---------------- Table Initialization and Resizing -------------- */
+
+    /**
+     * Returns a power of two table size for the given desired capacity.
+     * See Hackers Delight, sec 3.2
+     */
+    private static final int tableSizeFor(int c) {
+        int n = c - 1;
+        n |= n >>> 1;
+        n |= n >>> 2;
+        n |= n >>> 4;
+        n |= n >>> 8;
+        n |= n >>> 16;
+        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
+    }
+
+    /**
+     * Initializes table, using the size recorded in sizeCtl.
+     */
+    private final Node<K,V>[] initTable() {
+        Node<K,V>[] tab; int sc;
+        while ((tab = table) == null) {
+            if ((sc = sizeCtl) < 0)
+                Thread.yield(); // lost initialization race; just spin
+            else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
+                try {
+                    if ((tab = table) == null) {
+                        int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
+                        table = tab = (Node<K,V>[])new Node[n];
+                        sc = n - (n >>> 2);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+                break;
+            }
+        }
+        return tab;
+    }
+
+    /**
+     * Adds to count, and if table is too small and not already
+     * resizing, initiates transfer. If already resizing, helps
+     * perform transfer if work is available.  Rechecks occupancy
+     * after a transfer to see if another resize is already needed
+     * because resizings are lagging additions.
+     *
+     * @param x the count to add
+     * @param check if <0, don't check resize, if <= 1 only check if uncontended
+     */
+    private final void addCount(long x, int check) {
+        Cell[] as; long b, s;
+        if ((as = counterCells) != null ||
+            !U.compareAndSwapLong(this, BASECOUNT, b = baseCount, s = b + x)) {
+            Cell a; long v; int m;
+            boolean uncontended = true;
+            if (as == null || (m = as.length - 1) < 0 ||
+                (a = as[ThreadLocalRandom.getProbe() & m]) == null ||
+                !(uncontended =
+                  U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))) {
+                fullAddCount(x, uncontended);
+                return;
+            }
+            if (check <= 1)
+                return;
+            s = sumCount();
+        }
+        if (check >= 0) {
+            Node<K,V>[] tab, nt; int sc;
+            while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
+                   tab.length < MAXIMUM_CAPACITY) {
+                if (sc < 0) {
+                    if (sc == -1 || transferIndex <= transferOrigin ||
+                        (nt = nextTable) == null)
+                        break;
+                    if (U.compareAndSwapInt(this, SIZECTL, sc, sc - 1))
+                        transfer(tab, nt);
+                }
+                else if (U.compareAndSwapInt(this, SIZECTL, sc, -2))
+                    transfer(tab, null);
+                s = sumCount();
             }
         }
     }
 
-    // Accessing segments
-
     /**
-     * Gets the jth element of given segment array (if nonnull) with
-     * volatile element access semantics via Unsafe. (The null check
-     * can trigger harmlessly only during deserialization.) Note:
-     * because each element of segments array is set only once (using
-     * fully ordered writes), some performance-sensitive methods rely
-     * on this method only as a recheck upon null reads.
+     * Tries to presize table to accommodate the given number of elements.
+     *
+     * @param size number of elements (doesn't need to be perfectly accurate)
      */
-    @SuppressWarnings("unchecked")
-    static final <K,V> Segment<K,V> segmentAt(Segment<K,V>[] ss, int j) {
-        long u = (j << SSHIFT) + SBASE;
-        return ss == null ? null :
-            (Segment<K,V>) UNSAFE.getObjectVolatile(ss, u);
-    }
-
-    /**
-     * Returns the segment for the given index, creating it and
-     * recording in segment table (via CAS) if not already present.
-     *
-     * @param k the index
-     * @return the segment
-     */
-    @SuppressWarnings("unchecked")
-    private Segment<K,V> ensureSegment(int k) {
-        final Segment<K,V>[] ss = this.segments;
-        long u = (k << SSHIFT) + SBASE; // raw offset
-        Segment<K,V> seg;
-        if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) == null) {
-            Segment<K,V> proto = ss[0]; // use segment 0 as prototype
-            int cap = proto.table.length;
-            float lf = proto.loadFactor;
-            int threshold = (int)(cap * lf);
-            HashEntry<K,V>[] tab = (HashEntry<K,V>[])new HashEntry<?,?>[cap];
-            if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u))
-                == null) { // recheck
-                Segment<K,V> s = new Segment<K,V>(lf, threshold, tab);
-                while ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u))
-                       == null) {
-                    if (UNSAFE.compareAndSwapObject(ss, u, null, seg = s))
-                        break;
+    private final void tryPresize(int size) {
+        int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
+            tableSizeFor(size + (size >>> 1) + 1);
+        int sc;
+        while ((sc = sizeCtl) >= 0) {
+            Node<K,V>[] tab = table; int n;
+            if (tab == null || (n = tab.length) == 0) {
+                n = (sc > c) ? sc : c;
+                if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
+                    try {
+                        if (table == tab) {
+                            table = (Node<K,V>[])new Node[n];
+                            sc = n - (n >>> 2);
+                        }
+                    } finally {
+                        sizeCtl = sc;
+                    }
                 }
             }
+            else if (c <= sc || n >= MAXIMUM_CAPACITY)
+                break;
+            else if (tab == table &&
+                     U.compareAndSwapInt(this, SIZECTL, sc, -2))
+                transfer(tab, null);
         }
-        return seg;
     }
 
-    // Hash-based segment and entry accesses
-
     /**
-     * Gets the segment for the given hash code.
+     * Moves and/or copies the nodes in each bin to new table. See
+     * above for explanation.
      */
-    @SuppressWarnings("unchecked")
-    private Segment<K,V> segmentForHash(int h) {
-        long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE;
-        return (Segment<K,V>) UNSAFE.getObjectVolatile(segments, u);
+    private final void transfer(Node<K,V>[] tab, Node<K,V>[] nextTab) {
+        int n = tab.length, stride;
+        if ((stride = (NCPU > 1) ? (n >>> 3) / NCPU : n) < MIN_TRANSFER_STRIDE)
+            stride = MIN_TRANSFER_STRIDE; // subdivide range
+        if (nextTab == null) {            // initiating
+            try {
+                nextTab = (Node<K,V>[])new Node[n << 1];
+            } catch (Throwable ex) {      // try to cope with OOME
+                sizeCtl = Integer.MAX_VALUE;
+                return;
+            }
+            nextTable = nextTab;
+            transferOrigin = n;
+            transferIndex = n;
+            Node<K,V> rev = new Node<K,V>(MOVED, tab, null, null);
+            for (int k = n; k > 0;) {    // progressively reveal ready slots
+                int nextk = (k > stride) ? k - stride : 0;
+                for (int m = nextk; m < k; ++m)
+                    nextTab[m] = rev;
+                for (int m = n + nextk; m < n + k; ++m)
+                    nextTab[m] = rev;
+                U.putOrderedInt(this, TRANSFERORIGIN, k = nextk);
+            }
+        }
+        int nextn = nextTab.length;
+        Node<K,V> fwd = new Node<K,V>(MOVED, nextTab, null, null);
+        boolean advance = true;
+        for (int i = 0, bound = 0;;) {
+            int nextIndex, nextBound; Node<K,V> f; Object fk;
+            while (advance) {
+                if (--i >= bound)
+                    advance = false;
+                else if ((nextIndex = transferIndex) <= transferOrigin) {
+                    i = -1;
+                    advance = false;
+                }
+                else if (U.compareAndSwapInt
+                         (this, TRANSFERINDEX, nextIndex,
+                          nextBound = (nextIndex > stride ?
+                                       nextIndex - stride : 0))) {
+                    bound = nextBound;
+                    i = nextIndex - 1;
+                    advance = false;
+                }
+            }
+            if (i < 0 || i >= n || i + n >= nextn) {
+                for (int sc;;) {
+                    if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, ++sc)) {
+                        if (sc == -1) {
+                            nextTable = null;
+                            table = nextTab;
+                            sizeCtl = (n << 1) - (n >>> 1);
+                        }
+                        return;
+                    }
+                }
+            }
+            else if ((f = tabAt(tab, i)) == null) {
+                if (casTabAt(tab, i, null, fwd)) {
+                    setTabAt(nextTab, i, null);
+                    setTabAt(nextTab, i + n, null);
+                    advance = true;
+                }
+            }
+            else if (f.hash >= 0) {
+                synchronized (f) {
+                    if (tabAt(tab, i) == f) {
+                        int runBit = f.hash & n;
+                        Node<K,V> lastRun = f, lo = null, hi = null;
+                        for (Node<K,V> p = f.next; p != null; p = p.next) {
+                            int b = p.hash & n;
+                            if (b != runBit) {
+                                runBit = b;
+                                lastRun = p;
+                            }
+                        }
+                        if (runBit == 0)
+                            lo = lastRun;
+                        else
+                            hi = lastRun;
+                        for (Node<K,V> p = f; p != lastRun; p = p.next) {
+                            int ph = p.hash; Object pk = p.key; V pv = p.val;
+                            if ((ph & n) == 0)
+                                lo = new Node<K,V>(ph, pk, pv, lo);
+                            else
+                                hi = new Node<K,V>(ph, pk, pv, hi);
+                        }
+                        setTabAt(nextTab, i, lo);
+                        setTabAt(nextTab, i + n, hi);
+                        setTabAt(tab, i, fwd);
+                        advance = true;
+                    }
+                }
+            }
+            else if ((fk = f.key) instanceof TreeBin) {
+                TreeBin<K,V> t = (TreeBin<K,V>)fk;
+                long stamp = t.writeLock();
+                try {
+                    if (tabAt(tab, i) == f) {
+                        TreeNode<K,V> root;
+                        Node<K,V> ln = null, hn = null;
+                        if ((root = t.root) != null) {
+                            Node<K,V> e, p; TreeNode<K,V> lr, rr; int lh;
+                            TreeBin<K,V> lt = null, ht = null;
+                            for (lr = root; lr.left != null; lr = lr.left);
+                            for (rr = root; rr.right != null; rr = rr.right);
+                            if ((lh = lr.hash) == rr.hash) { // move entire tree
+                                if ((lh & n) == 0)
+                                    lt = t;
+                                else
+                                    ht = t;
+                            }
+                            else {
+                                lt = new TreeBin<K,V>();
+                                ht = new TreeBin<K,V>();
+                                int lc = 0, hc = 0;
+                                for (e = t.first; e != null; e = e.next) {
+                                    int h = e.hash;
+                                    Object k = e.key; V v = e.val;
+                                    if ((h & n) == 0) {
+                                        ++lc;
+                                        lt.putTreeNode(h, k, v);
+                                    }
+                                    else {
+                                        ++hc;
+                                        ht.putTreeNode(h, k, v);
+                                    }
+                                }
+                                if (lc < TREE_THRESHOLD) { // throw away
+                                    for (p = lt.first; p != null; p = p.next)
+                                        ln = new Node<K,V>(p.hash, p.key,
+                                                           p.val, ln);
+                                    lt = null;
+                                }
+                                if (hc < TREE_THRESHOLD) {
+                                    for (p = ht.first; p != null; p = p.next)
+                                        hn = new Node<K,V>(p.hash, p.key,
+                                                           p.val, hn);
+                                    ht = null;
+                                }
+                            }
+                            if (ln == null && lt != null)
+                                ln = new Node<K,V>(MOVED, lt, null, null);
+                            if (hn == null && ht != null)
+                                hn = new Node<K,V>(MOVED, ht, null, null);
+                        }
+                        setTabAt(nextTab, i, ln);
+                        setTabAt(nextTab, i + n, hn);
+                        setTabAt(tab, i, fwd);
+                        advance = true;
+                    }
+                } finally {
+                    t.unlockWrite(stamp);
+                }
+            }
+            else
+                advance = true; // already processed
+        }
     }
 
+    /* ---------------- Counter support -------------- */
+
+    final long sumCount() {
+        Cell[] as = counterCells; Cell a;
+        long sum = baseCount;
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null)
+                    sum += a.value;
+            }
+        }
+        return sum;
+    }
+
+    // See LongAdder version for explanation
+    private final void fullAddCount(long x, boolean wasUncontended) {
+        int h;
+        if ((h = ThreadLocalRandom.getProbe()) == 0) {
+            ThreadLocalRandom.localInit();      // force initialization
+            h = ThreadLocalRandom.getProbe();
+            wasUncontended = true;
+        }
+        boolean collide = false;                // True if last slot nonempty
+        for (;;) {
+            Cell[] as; Cell a; int n; long v;
+            if ((as = counterCells) != null && (n = as.length) > 0) {
+                if ((a = as[(n - 1) & h]) == null) {
+                    if (cellsBusy == 0) {            // Try to attach new Cell
+                        Cell r = new Cell(x); // Optimistic create
+                        if (cellsBusy == 0 &&
+                            U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) {
+                            boolean created = false;
+                            try {               // Recheck under lock
+                                Cell[] rs; int m, j;
+                                if ((rs = counterCells) != null &&
+                                    (m = rs.length) > 0 &&
+                                    rs[j = (m - 1) & h] == null) {
+                                    rs[j] = r;
+                                    created = true;
+                                }
+                            } finally {
+                                cellsBusy = 0;
+                            }
+                            if (created)
+                                break;
+                            continue;           // Slot is now non-empty
+                        }
+                    }
+                    collide = false;
+                }
+                else if (!wasUncontended)       // CAS already known to fail
+                    wasUncontended = true;      // Continue after rehash
+                else if (U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))
+                    break;
+                else if (counterCells != as || n >= NCPU)
+                    collide = false;            // At max size or stale
+                else if (!collide)
+                    collide = true;
+                else if (cellsBusy == 0 &&
+                         U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) {
+                    try {
+                        if (counterCells == as) {// Expand table unless stale
+                            Cell[] rs = new Cell[n << 1];
+                            for (int i = 0; i < n; ++i)
+                                rs[i] = as[i];
+                            counterCells = rs;
+                        }
+                    } finally {
+                        cellsBusy = 0;
+                    }
+                    collide = false;
+                    continue;                   // Retry with expanded table
+                }
+                h = ThreadLocalRandom.advanceProbe(h);
+            }
+            else if (cellsBusy == 0 && counterCells == as &&
+                     U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) {
+                boolean init = false;
+                try {                           // Initialize table
+                    if (counterCells == as) {
+                        Cell[] rs = new Cell[2];
+                        rs[h & 1] = new Cell(x);
+                        counterCells = rs;
+                        init = true;
+                    }
+                } finally {
+                    cellsBusy = 0;
+                }
+                if (init)
+                    break;
+            }
+            else if (U.compareAndSwapLong(this, BASECOUNT, v = baseCount, v + x))
+                break;                          // Fall back on using base
+        }
+    }
+
+    /* ----------------Table Traversal -------------- */
+
     /**
-     * Gets the table entry for the given segment and hash code.
+     * Encapsulates traversal for methods such as containsValue; also
+     * serves as a base class for other iterators and spliterators.
+     *
+     * Method advance visits once each still-valid node that was
+     * reachable upon iterator construction. It might miss some that
+     * were added to a bin after the bin was visited, which is OK wrt
+     * consistency guarantees. Maintaining this property in the face
+     * of possible ongoing resizes requires a fair amount of
+     * bookkeeping state that is difficult to optimize away amidst
+     * volatile accesses.  Even so, traversal maintains reasonable
+     * throughput.
+     *
+     * Normally, iteration proceeds bin-by-bin traversing lists.
+     * However, if the table has been resized, then all future steps
+     * must traverse both the bin at the current index as well as at
+     * (index + baseSize); and so on for further resizings. To
+     * paranoically cope with potential sharing by users of iterators
+     * across threads, iteration terminates if a bounds checks fails
+     * for a table read.
      */
-    @SuppressWarnings("unchecked")
-    static final <K,V> HashEntry<K,V> entryForHash(Segment<K,V> seg, int h) {
-        HashEntry<K,V>[] tab;
-        return (seg == null || (tab = seg.table) == null) ? null :
-            (HashEntry<K,V>) UNSAFE.getObjectVolatile
-            (tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE);
+    static class Traverser<K,V> {
+        Node<K,V>[] tab;        // current table; updated if resized
+        Node<K,V> next;         // the next entry to use
+        int index;              // index of bin to use next
+        int baseIndex;          // current index of initial table
+        int baseLimit;          // index bound for initial table
+        final int baseSize;     // initial table size
+
+        Traverser(Node<K,V>[] tab, int size, int index, int limit) {
+            this.tab = tab;
+            this.baseSize = size;
+            this.baseIndex = this.index = index;
+            this.baseLimit = limit;
+            this.next = null;
+        }
+
+        /**
+         * Advances if possible, returning next valid node, or null if none.
+         */
+        final Node<K,V> advance() {
+            Node<K,V> e;
+            if ((e = next) != null)
+                e = e.next;
+            for (;;) {
+                Node<K,V>[] t; int i, n; Object ek;  // must use locals in checks
+                if (e != null)
+                    return next = e;
+                if (baseIndex >= baseLimit || (t = tab) == null ||
+                    (n = t.length) <= (i = index) || i < 0)
+                    return next = null;
+                if ((e = tabAt(t, index)) != null && e.hash < 0) {
+                    if ((ek = e.key) instanceof TreeBin)
+                        e = ((TreeBin<K,V>)ek).first;
+                    else {
+                        tab = (Node<K,V>[])ek;
+                        e = null;
+                        continue;
+                    }
+                }
+                if ((index += baseSize) >= n)
+                    index = ++baseIndex;    // visit upper slots if present
+            }
+        }
     }
 
+    /**
+     * Base of key, value, and entry Iterators. Adds fields to
+     * Traverser to support iterator.remove
+     */
+    static class BaseIterator<K,V> extends Traverser<K,V> {
+        final ConcurrentHashMap<K,V> map;
+        Node<K,V> lastReturned;
+        BaseIterator(Node<K,V>[] tab, int size, int index, int limit,
+                    ConcurrentHashMap<K,V> map) {
+            super(tab, size, index, limit);
+            this.map = map;
+            advance();
+        }
+
+        public final boolean hasNext() { return next != null; }
+        public final boolean hasMoreElements() { return next != null; }
+
+        public final void remove() {
+            Node<K,V> p;
+            if ((p = lastReturned) == null)
+                throw new IllegalStateException();
+            lastReturned = null;
+            map.internalReplace((K)p.key, null, null);
+        }
+    }
+
+    static final class KeyIterator<K,V> extends BaseIterator<K,V>
+        implements Iterator<K>, Enumeration<K> {
+        KeyIterator(Node<K,V>[] tab, int index, int size, int limit,
+                    ConcurrentHashMap<K,V> map) {
+            super(tab, index, size, limit, map);
+        }
+
+        public final K next() {
+            Node<K,V> p;
+            if ((p = next) == null)
+                throw new NoSuchElementException();
+            K k = (K)p.key;
+            lastReturned = p;
+            advance();
+            return k;
+        }
+
+        public final K nextElement() { return next(); }
+    }
+
+    static final class ValueIterator<K,V> extends BaseIterator<K,V>
+        implements Iterator<V>, Enumeration<V> {
+        ValueIterator(Node<K,V>[] tab, int index, int size, int limit,
+                      ConcurrentHashMap<K,V> map) {
+            super(tab, index, size, limit, map);
+        }
+
+        public final V next() {
+            Node<K,V> p;
+            if ((p = next) == null)
+                throw new NoSuchElementException();
+            V v = p.val;
+            lastReturned = p;
+            advance();
+            return v;
+        }
+
+        public final V nextElement() { return next(); }
+    }
+
+    static final class EntryIterator<K,V> extends BaseIterator<K,V>
+        implements Iterator<Map.Entry<K,V>> {
+        EntryIterator(Node<K,V>[] tab, int index, int size, int limit,
+                      ConcurrentHashMap<K,V> map) {
+            super(tab, index, size, limit, map);
+        }
+
+        public final Map.Entry<K,V> next() {
+            Node<K,V> p;
+            if ((p = next) == null)
+                throw new NoSuchElementException();
+            K k = (K)p.key;
+            V v = p.val;
+            lastReturned = p;
+            advance();
+            return new MapEntry<K,V>(k, v, map);
+        }
+    }
+
+    static final class KeySpliterator<K,V> extends Traverser<K,V>
+        implements Spliterator<K> {
+        long est;               // size estimate
+        KeySpliterator(Node<K,V>[] tab, int size, int index, int limit,
+                       long est) {
+            super(tab, size, index, limit);
+            this.est = est;
+        }
+
+        public Spliterator<K> trySplit() {
+            int i, f, h;
+            return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
+                new KeySpliterator<K,V>(tab, baseSize, baseLimit = h,
+                                        f, est >>>= 1);
+        }
+
+        public void forEachRemaining(Consumer<? super K> action) {
+            if (action == null) throw new NullPointerException();
+            for (Node<K,V> p; (p = advance()) != null;)
+                action.accept((K)p.key);
+        }
+
+        public boolean tryAdvance(Consumer<? super K> action) {
+            if (action == null) throw new NullPointerException();
+            Node<K,V> p;
+            if ((p = advance()) == null)
+                return false;
+            action.accept((K)p.key);
+            return true;
+        }
+
+        public long estimateSize() { return est; }
+
+        public int characteristics() {
+            return Spliterator.DISTINCT | Spliterator.CONCURRENT |
+                Spliterator.NONNULL;
+        }
+    }
+
+    static final class ValueSpliterator<K,V> extends Traverser<K,V>
+        implements Spliterator<V> {
+        long est;               // size estimate
+        ValueSpliterator(Node<K,V>[] tab, int size, int index, int limit,
+                         long est) {
+            super(tab, size, index, limit);
+            this.est = est;
+        }
+
+        public Spliterator<V> trySplit() {
+            int i, f, h;
+            return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
+                new ValueSpliterator<K,V>(tab, baseSize, baseLimit = h,
+                                          f, est >>>= 1);
+        }
+
+        public void forEachRemaining(Consumer<? super V> action) {
+            if (action == null) throw new NullPointerException();
+            for (Node<K,V> p; (p = advance()) != null;)
+                action.accept(p.val);
+        }
+
+        public boolean tryAdvance(Consumer<? super V> action) {
+            if (action == null) throw new NullPointerException();
+            Node<K,V> p;
+            if ((p = advance()) == null)
+                return false;
+            action.accept(p.val);
+            return true;
+        }
+
+        public long estimateSize() { return est; }
+
+        public int characteristics() {
+            return Spliterator.CONCURRENT | Spliterator.NONNULL;
+        }
+    }
+
+    static final class EntrySpliterator<K,V> extends Traverser<K,V>
+        implements Spliterator<Map.Entry<K,V>> {
+        final ConcurrentHashMap<K,V> map; // To export MapEntry
+        long est;               // size estimate
+        EntrySpliterator(Node<K,V>[] tab, int size, int index, int limit,
+                         long est, ConcurrentHashMap<K,V> map) {
+            super(tab, size, index, limit);
+            this.map = map;
+            this.est = est;
+        }
+
+        public Spliterator<Map.Entry<K,V>> trySplit() {
+            int i, f, h;
+            return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
+                new EntrySpliterator<K,V>(tab, baseSize, baseLimit = h,
+                                          f, est >>>= 1, map);
+        }
+
+        public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
+            if (action == null) throw new NullPointerException();
+            for (Node<K,V> p; (p = advance()) != null; )
+                action.accept(new MapEntry<K,V>((K)p.key, p.val, map));
+        }
+
+        public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
+            if (action == null) throw new NullPointerException();
+            Node<K,V> p;
+            if ((p = advance()) == null)
+                return false;
+            action.accept(new MapEntry<K,V>((K)p.key, p.val, map));
+            return true;
+        }
+
+        public long estimateSize() { return est; }
+
+        public int characteristics() {
+            return Spliterator.DISTINCT | Spliterator.CONCURRENT |
+                Spliterator.NONNULL;
+        }
+    }
+
+
     /* ---------------- Public operations -------------- */
 
     /**
-     * Creates a new, empty map with the specified initial
-     * capacity, load factor and concurrency level.
-     *
-     * @param initialCapacity the initial capacity. The implementation
-     * performs internal sizing to accommodate this many elements.
-     * @param loadFactor  the load factor threshold, used to control resizing.
-     * Resizing may be performed when the average number of elements per
-     * bin exceeds this threshold.
-     * @param concurrencyLevel the estimated number of concurrently
-     * updating threads. The implementation performs internal sizing
-     * to try to accommodate this many threads.
-     * @throws IllegalArgumentException if the initial capacity is
-     * negative or the load factor or concurrencyLevel are
-     * nonpositive.
+     * Creates a new, empty map with the default initial table size (16).
      */
-    @SuppressWarnings("unchecked")
-    public ConcurrentHashMap(int initialCapacity,
-                             float loadFactor, int concurrencyLevel) {
-        if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0)
-            throw new IllegalArgumentException();
-        if (concurrencyLevel > MAX_SEGMENTS)
-            concurrencyLevel = MAX_SEGMENTS;
-        // Find power-of-two sizes best matching arguments
-        int sshift = 0;
-        int ssize = 1;
-        while (ssize < concurrencyLevel) {
-            ++sshift;
-            ssize <<= 1;
-        }
-        this.segmentShift = 32 - sshift;
-        this.segmentMask = ssize - 1;
-        if (initialCapacity > MAXIMUM_CAPACITY)
-            initialCapacity = MAXIMUM_CAPACITY;
-        int c = initialCapacity / ssize;
-        if (c * ssize < initialCapacity)
-            ++c;
-        int cap = MIN_SEGMENT_TABLE_CAPACITY;
-        while (cap < c)
-            cap <<= 1;
-        // create segments and segments[0]
-        Segment<K,V> s0 =
-            new Segment<K,V>(loadFactor, (int)(cap * loadFactor),
-                             (HashEntry<K,V>[])new HashEntry<?,?>[cap]);
-        Segment<K,V>[] ss = (Segment<K,V>[])new Segment<?,?>[ssize];
-        UNSAFE.putOrderedObject(ss, SBASE, s0); // ordered write of segments[0]
-        this.segments = ss;
+    public ConcurrentHashMap() {
     }
 
     /**
-     * Creates a new, empty map with the specified initial capacity
-     * and load factor and with the default concurrencyLevel (16).
+     * Creates a new, empty map with an initial table size
+     * accommodating the specified number of elements without the need
+     * to dynamically resize.
      *
      * @param initialCapacity The implementation performs internal
      * sizing to accommodate this many elements.
-     * @param loadFactor  the load factor threshold, used to control resizing.
-     * Resizing may be performed when the average number of elements per
-     * bin exceeds this threshold.
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative
+     */
+    public ConcurrentHashMap(int initialCapacity) {
+        if (initialCapacity < 0)
+            throw new IllegalArgumentException();
+        int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
+                   MAXIMUM_CAPACITY :
+                   tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));
+        this.sizeCtl = cap;
+    }
+
+    /**
+     * Creates a new map with the same mappings as the given map.
+     *
+     * @param m the map
+     */
+    public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
+        this.sizeCtl = DEFAULT_CAPACITY;
+        internalPutAll(m);
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size based on
+     * the given number of elements ({@code initialCapacity}) and
+     * initial table density ({@code loadFactor}).
+     *
+     * @param initialCapacity the initial capacity. The implementation
+     * performs internal sizing to accommodate this many elements,
+     * given the specified load factor.
+     * @param loadFactor the load factor (table density) for
+     * establishing the initial table size
      * @throws IllegalArgumentException if the initial capacity of
      * elements is negative or the load factor is nonpositive
      *
      * @since 1.6
      */
     public ConcurrentHashMap(int initialCapacity, float loadFactor) {
-        this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL);
+        this(initialCapacity, loadFactor, 1);
     }
 
     /**
-     * Creates a new, empty map with the specified initial capacity,
-     * and with default load factor (0.75) and concurrencyLevel (16).
+     * Creates a new, empty map with an initial table size based on
+     * the given number of elements ({@code initialCapacity}), table
+     * density ({@code loadFactor}), and number of concurrently
+     * updating threads ({@code concurrencyLevel}).
      *
      * @param initialCapacity the initial capacity. The implementation
-     * performs internal sizing to accommodate this many elements.
+     * performs internal sizing to accommodate this many elements,
+     * given the specified load factor.
+     * @param loadFactor the load factor (table density) for
+     * establishing the initial table size
+     * @param concurrencyLevel the estimated number of concurrently
+     * updating threads. The implementation may use this value as
+     * a sizing hint.
+     * @throws IllegalArgumentException if the initial capacity is
+     * negative or the load factor or concurrencyLevel are
+     * nonpositive
+     */
+    public ConcurrentHashMap(int initialCapacity,
+                             float loadFactor, int concurrencyLevel) {
+        if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
+            throw new IllegalArgumentException();
+        if (initialCapacity < concurrencyLevel)   // Use at least as many bins
+            initialCapacity = concurrencyLevel;   // as estimated threads
+        long size = (long)(1.0 + (long)initialCapacity / loadFactor);
+        int cap = (size >= (long)MAXIMUM_CAPACITY) ?
+            MAXIMUM_CAPACITY : tableSizeFor((int)size);
+        this.sizeCtl = cap;
+    }
+
+    /**
+     * Creates a new {@link Set} backed by a ConcurrentHashMap
+     * from the given type to {@code Boolean.TRUE}.
+     *
+     * @return the new set
+     */
+    public static <K> KeySetView<K,Boolean> newKeySet() {
+        return new KeySetView<K,Boolean>
+            (new ConcurrentHashMap<K,Boolean>(), Boolean.TRUE);
+    }
+
+    /**
+     * Creates a new {@link Set} backed by a ConcurrentHashMap
+     * from the given type to {@code Boolean.TRUE}.
+     *
+     * @param initialCapacity The implementation performs internal
+     * sizing to accommodate this many elements.
      * @throws IllegalArgumentException if the initial capacity of
-     * elements is negative.
+     * elements is negative
+     * @return the new set
      */
-    public ConcurrentHashMap(int initialCapacity) {
-        this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
-    }
-
-    /**
-     * Creates a new, empty map with a default initial capacity (16),
-     * load factor (0.75) and concurrencyLevel (16).
-     */
-    public ConcurrentHashMap() {
-        this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
-    }
-
-    /**
-     * Creates a new map with the same mappings as the given map.
-     * The map is created with a capacity of 1.5 times the number
-     * of mappings in the given map or 16 (whichever is greater),
-     * and a default load factor (0.75) and concurrencyLevel (16).
-     *
-     * @param m the map
-     */
-    public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
-        this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
-                      DEFAULT_INITIAL_CAPACITY),
-             DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
-        putAll(m);
+    public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
+        return new KeySetView<K,Boolean>
+            (new ConcurrentHashMap<K,Boolean>(initialCapacity), Boolean.TRUE);
     }
 
     /**
@@ -834,38 +2637,7 @@
      * @return {@code true} if this map contains no key-value mappings
      */
     public boolean isEmpty() {
-        /*
-         * Sum per-segment modCounts to avoid mis-reporting when
-         * elements are concurrently added and removed in one segment
-         * while checking another, in which case the table was never
-         * actually empty at any point. (The sum ensures accuracy up
-         * through at least 1<<31 per-segment modifications before
-         * recheck.)  Methods size() and containsValue() use similar
-         * constructions for stability checks.
-         */
-        long sum = 0L;
-        final Segment<K,V>[] segments = this.segments;
-        for (int j = 0; j < segments.length; ++j) {
-            Segment<K,V> seg = segmentAt(segments, j);
-            if (seg != null) {
-                if (seg.count != 0)
-                    return false;
-                sum += seg.modCount;
-            }
-        }
-        if (sum != 0L) { // recheck unless no modifications
-            for (int j = 0; j < segments.length; ++j) {
-                Segment<K,V> seg = segmentAt(segments, j);
-                if (seg != null) {
-                    if (seg.count != 0)
-                        return false;
-                    sum -= seg.modCount;
-                }
-            }
-            if (sum != 0L)
-                return false;
-        }
-        return true;
+        return sumCount() <= 0L; // ignore transient negative values
     }
 
     /**
@@ -876,43 +2648,24 @@
      * @return the number of key-value mappings in this map
      */
     public int size() {
-        // Try a few times to get accurate count. On failure due to
-        // continuous async changes in table, resort to locking.
-        final Segment<K,V>[] segments = this.segments;
-        int size;
-        boolean overflow; // true if size overflows 32 bits
-        long sum;         // sum of modCounts
-        long last = 0L;   // previous sum
-        int retries = -1; // first iteration isn't retry
-        try {
-            for (;;) {
-                if (retries++ == RETRIES_BEFORE_LOCK) {
-                    for (int j = 0; j < segments.length; ++j)
-                        ensureSegment(j).lock(); // force creation
-                }
-                sum = 0L;
-                size = 0;
-                overflow = false;
-                for (int j = 0; j < segments.length; ++j) {
-                    Segment<K,V> seg = segmentAt(segments, j);
-                    if (seg != null) {
-                        sum += seg.modCount;
-                        int c = seg.count;
-                        if (c < 0 || (size += c) < 0)
-                            overflow = true;
-                    }
-                }
-                if (sum == last)
-                    break;
-                last = sum;
-            }
-        } finally {
-            if (retries > RETRIES_BEFORE_LOCK) {
-                for (int j = 0; j < segments.length; ++j)
-                    segmentAt(segments, j).unlock();
-            }
-        }
-        return overflow ? Integer.MAX_VALUE : size;
+        long n = sumCount();
+        return ((n < 0L) ? 0 :
+                (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
+                (int)n);
+    }
+
+    /**
+     * Returns the number of mappings. This method should be used
+     * instead of {@link #size} because a ConcurrentHashMap may
+     * contain more mappings than can be represented as an int. The
+     * value returned is an estimate; the actual count may differ if
+     * there are concurrent insertions or removals.
+     *
+     * @return the number of mappings
+     */
+    public long mappingCount() {
+        long n = sumCount();
+        return (n < 0L) ? 0L : n; // ignore transient negative values
     }
 
     /**
@@ -926,23 +2679,24 @@
      *
      * @throws NullPointerException if the specified key is null
      */
-    @SuppressWarnings("unchecked")
     public V get(Object key) {
-        Segment<K,V> s; // manually integrate access methods to reduce overhead
-        HashEntry<K,V>[] tab;
-        int h = hash(key);
-        long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE;
-        if ((s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)) != null &&
-            (tab = s.table) != null) {
-            for (HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile
-                     (tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE);
-                 e != null; e = e.next) {
-                K k;
-                if ((k = e.key) == key || (e.hash == h && key.equals(k)))
-                    return e.value;
-            }
-        }
-        return null;
+        return internalGet(key);
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped, or the
+     * given default value if this map contains no mapping for the
+     * key.
+     *
+     * @param key the key whose associated value is to be returned
+     * @param defaultValue the value to return if this map contains
+     * no mapping for the given key
+     * @return the mapping for the key, if present; else the default value
+     * @throws NullPointerException if the specified key is null
+     */
+    public V getOrDefault(Object key, V defaultValue) {
+        V v;
+        return (v = internalGet(key)) == null ? defaultValue : v;
     }
 
     /**
@@ -954,29 +2708,14 @@
      *         {@code equals} method; {@code false} otherwise
      * @throws NullPointerException if the specified key is null
      */
-    @SuppressWarnings("unchecked")
     public boolean containsKey(Object key) {
-        Segment<K,V> s; // same as get() except no need for volatile value read
-        HashEntry<K,V>[] tab;
-        int h = hash(key);
-        long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE;
-        if ((s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)) != null &&
-            (tab = s.table) != null) {
-            for (HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile
-                     (tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE);
-                 e != null; e = e.next) {
-                K k;
-                if ((k = e.key) == key || (e.hash == h && key.equals(k)))
-                    return true;
-            }
-        }
-        return false;
+        return internalGet(key) != null;
     }
 
     /**
      * Returns {@code true} if this map maps one or more keys to the
-     * specified value. Note: This method requires a full traversal
-     * of the map, and so is much slower than method {@code containsKey}.
+     * specified value. Note: This method may require a full traversal
+     * of the map, and is much slower than method {@code containsKey}.
      *
      * @param value value whose presence in this map is to be tested
      * @return {@code true} if this map maps one or more keys to the
@@ -984,49 +2723,18 @@
      * @throws NullPointerException if the specified value is null
      */
     public boolean containsValue(Object value) {
-        // Same idea as size()
         if (value == null)
             throw new NullPointerException();
-        final Segment<K,V>[] segments = this.segments;
-        boolean found = false;
-        long last = 0;
-        int retries = -1;
-        try {
-            outer: for (;;) {
-                if (retries++ == RETRIES_BEFORE_LOCK) {
-                    for (int j = 0; j < segments.length; ++j)
-                        ensureSegment(j).lock(); // force creation
-                }
-                long hashSum = 0L;
-                int sum = 0;
-                for (int j = 0; j < segments.length; ++j) {
-                    HashEntry<K,V>[] tab;
-                    Segment<K,V> seg = segmentAt(segments, j);
-                    if (seg != null && (tab = seg.table) != null) {
-                        for (int i = 0 ; i < tab.length; i++) {
-                            HashEntry<K,V> e;
-                            for (e = entryAt(tab, i); e != null; e = e.next) {
-                                V v = e.value;
-                                if (v != null && value.equals(v)) {
-                                    found = true;
-                                    break outer;
-                                }
-                            }
-                        }
-                        sum += seg.modCount;
-                    }
-                }
-                if (retries > 0 && sum == last)
-                    break;
-                last = sum;
-            }
-        } finally {
-            if (retries > RETRIES_BEFORE_LOCK) {
-                for (int j = 0; j < segments.length; ++j)
-                    segmentAt(segments, j).unlock();
+        Node<K,V>[] t;
+        if ((t = table) != null) {
+            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+            for (Node<K,V> p; (p = it.advance()) != null; ) {
+                V v;
+                if ((v = p.val) == value || value.equals(v))
+                    return true;
             }
         }
-        return found;
+        return false;
     }
 
     /**
@@ -1061,17 +2769,8 @@
      *         {@code null} if there was no mapping for {@code key}
      * @throws NullPointerException if the specified key or value is null
      */
-    @SuppressWarnings("unchecked")
     public V put(K key, V value) {
-        Segment<K,V> s;
-        if (value == null)
-            throw new NullPointerException();
-        int hash = hash(key);
-        int j = (hash >>> segmentShift) & segmentMask;
-        if ((s = (Segment<K,V>)UNSAFE.getObject          // nonvolatile; recheck
-             (segments, (j << SSHIFT) + SBASE)) == null) //  in ensureSegment
-            s = ensureSegment(j);
-        return s.put(key, hash, value, false);
+        return internalPut(key, value, false);
     }
 
     /**
@@ -1081,17 +2780,8 @@
      *         or {@code null} if there was no mapping for the key
      * @throws NullPointerException if the specified key or value is null
      */
-    @SuppressWarnings("unchecked")
     public V putIfAbsent(K key, V value) {
-        Segment<K,V> s;
-        if (value == null)
-            throw new NullPointerException();
-        int hash = hash(key);
-        int j = (hash >>> segmentShift) & segmentMask;
-        if ((s = (Segment<K,V>)UNSAFE.getObject
-             (segments, (j << SSHIFT) + SBASE)) == null)
-            s = ensureSegment(j);
-        return s.put(key, hash, value, true);
+        return internalPut(key, value, true);
     }
 
     /**
@@ -1102,8 +2792,105 @@
      * @param m mappings to be stored in this map
      */
     public void putAll(Map<? extends K, ? extends V> m) {
-        for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
-            put(e.getKey(), e.getValue());
+        internalPutAll(m);
+    }
+
+    /**
+     * If the specified key is not already associated with a value,
+     * attempts to compute its value using the given mapping function
+     * and enters it into this map unless {@code null}.  The entire
+     * method invocation is performed atomically, so the function is
+     * applied at most once per key.  Some attempted update operations
+     * on this map by other threads may be blocked while computation
+     * is in progress, so the computation should be short and simple,
+     * and must not attempt to update any other mappings of this map.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param mappingFunction the function to compute a value
+     * @return the current (existing or computed) value associated with
+     *         the specified key, or null if the computed value is null
+     * @throws NullPointerException if the specified key or mappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the mappingFunction does so,
+     *         in which case the mapping is left unestablished
+     */
+    public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
+        return internalComputeIfAbsent(key, mappingFunction);
+    }
+
+    /**
+     * If the value for the specified key is present, attempts to
+     * compute a new mapping given the key and its current mapped
+     * value.  The entire method invocation is performed atomically.
+     * Some attempted update operations on this map by other threads
+     * may be blocked while computation is in progress, so the
+     * computation should be short and simple, and must not attempt to
+     * update any other mappings of this map.
+     *
+     * @param key key with which a value may be associated
+     * @param remappingFunction the function to compute a value
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or remappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+        return internalCompute(key, true, remappingFunction);
+    }
+
+    /**
+     * Attempts to compute a mapping for the specified key and its
+     * current mapped value (or {@code null} if there is no current
+     * mapping). The entire method invocation is performed atomically.
+     * Some attempted update operations on this map by other threads
+     * may be blocked while computation is in progress, so the
+     * computation should be short and simple, and must not attempt to
+     * update any other mappings of this Map.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param remappingFunction the function to compute a value
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or remappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+        return internalCompute(key, false, remappingFunction);
+    }
+
+    /**
+     * If the specified key is not already associated with a
+     * (non-null) value, associates it with the given value.
+     * Otherwise, replaces the value with the results of the given
+     * remapping function, or removes if {@code null}. The entire
+     * method invocation is performed atomically.  Some attempted
+     * update operations on this map by other threads may be blocked
+     * while computation is in progress, so the computation should be
+     * short and simple, and must not attempt to update any other
+     * mappings of this Map.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param value the value to use if absent
+     * @param remappingFunction the function to recompute a value if present
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or the
+     *         remappingFunction is null
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+        return internalMerge(key, value, remappingFunction);
     }
 
     /**
@@ -1116,9 +2903,7 @@
      * @throws NullPointerException if the specified key is null
      */
     public V remove(Object key) {
-        int hash = hash(key);
-        Segment<K,V> s = segmentForHash(hash);
-        return s == null ? null : s.remove(key, hash, null);
+        return internalReplace(key, null, null);
     }
 
     /**
@@ -1127,10 +2912,9 @@
      * @throws NullPointerException if the specified key is null
      */
     public boolean remove(Object key, Object value) {
-        int hash = hash(key);
-        Segment<K,V> s;
-        return value != null && (s = segmentForHash(hash)) != null &&
-            s.remove(key, hash, value) != null;
+        if (key == null)
+            throw new NullPointerException();
+        return value != null && internalReplace(key, null, value) != null;
     }
 
     /**
@@ -1139,11 +2923,9 @@
      * @throws NullPointerException if any of the arguments are null
      */
     public boolean replace(K key, V oldValue, V newValue) {
-        int hash = hash(key);
-        if (oldValue == null || newValue == null)
+        if (key == null || oldValue == null || newValue == null)
             throw new NullPointerException();
-        Segment<K,V> s = segmentForHash(hash);
-        return s != null && s.replace(key, hash, oldValue, newValue);
+        return internalReplace(key, newValue, oldValue) != null;
     }
 
     /**
@@ -1154,23 +2936,16 @@
      * @throws NullPointerException if the specified key or value is null
      */
     public V replace(K key, V value) {
-        int hash = hash(key);
-        if (value == null)
+        if (key == null || value == null)
             throw new NullPointerException();
-        Segment<K,V> s = segmentForHash(hash);
-        return s == null ? null : s.replace(key, hash, value);
+        return internalReplace(key, value, null);
     }
 
     /**
      * Removes all of the mappings from this map.
      */
     public void clear() {
-        final Segment<K,V>[] segments = this.segments;
-        for (int j = 0; j < segments.length; ++j) {
-            Segment<K,V> s = segmentAt(segments, j);
-            if (s != null)
-                s.clear();
-        }
+        internalClear();
     }
 
     /**
@@ -1188,10 +2963,29 @@
      * and guarantees to traverse elements as they existed upon
      * construction of the iterator, and may (but is not guaranteed to)
      * reflect any modifications subsequent to construction.
+     *
+     * @return the set view
      */
-    public Set<K> keySet() {
-        Set<K> ks = keySet;
-        return (ks != null) ? ks : (keySet = new KeySet());
+    public KeySetView<K,V> keySet() {
+        KeySetView<K,V> ks = keySet;
+        return (ks != null) ? ks : (keySet = new KeySetView<K,V>(this, null));
+    }
+
+    /**
+     * Returns a {@link Set} view of the keys in this map, using the
+     * given common mapped value for any additions (i.e., {@link
+     * Collection#add} and {@link Collection#addAll(Collection)}).
+     * This is of course only appropriate if it is acceptable to use
+     * the same value for all additions from this view.
+     *
+     * @param mappedValue the mapped value to use for any additions
+     * @return the set view
+     * @throws NullPointerException if the mappedValue is null
+     */
+    public KeySetView<K,V> keySet(V mappedValue) {
+        if (mappedValue == null)
+            throw new NullPointerException();
+        return new KeySetView<K,V>(this, mappedValue);
     }
 
     /**
@@ -1209,10 +3003,12 @@
      * and guarantees to traverse elements as they existed upon
      * construction of the iterator, and may (but is not guaranteed to)
      * reflect any modifications subsequent to construction.
+     *
+     * @return the collection view
      */
     public Collection<V> values() {
-        Collection<V> vs = values;
-        return (vs != null) ? vs : (values = new Values());
+        ValuesView<K,V> vs = values;
+        return (vs != null) ? vs : (values = new ValuesView<K,V>(this));
     }
 
     /**
@@ -1222,18 +3018,19 @@
      * removal, which removes the corresponding mapping from the map,
      * via the {@code Iterator.remove}, {@code Set.remove},
      * {@code removeAll}, {@code retainAll}, and {@code clear}
-     * operations.  It does not support the {@code add} or
-     * {@code addAll} operations.
+     * operations.
      *
      * <p>The view's {@code iterator} is a "weakly consistent" iterator
      * that will never throw {@link ConcurrentModificationException},
      * and guarantees to traverse elements as they existed upon
      * construction of the iterator, and may (but is not guaranteed to)
      * reflect any modifications subsequent to construction.
+     *
+     * @return the set view
      */
     public Set<Map.Entry<K,V>> entrySet() {
-        Set<Map.Entry<K,V>> es = entrySet;
-        return (es != null) ? es : (entrySet = new EntrySet());
+        EntrySetView<K,V> es = entrySet;
+        return (es != null) ? es : (entrySet = new EntrySetView<K,V>(this));
     }
 
     /**
@@ -1243,7 +3040,9 @@
      * @see #keySet()
      */
     public Enumeration<K> keys() {
-        return new KeyIterator();
+        Node<K,V>[] t;
+        int f = (t = table) == null ? 0 : t.length;
+        return new KeyIterator<K,V>(t, f, 0, f, this);
     }
 
     /**
@@ -1253,191 +3052,110 @@
      * @see #values()
      */
     public Enumeration<V> elements() {
-        return new ValueIterator();
+        Node<K,V>[] t;
+        int f = (t = table) == null ? 0 : t.length;
+        return new ValueIterator<K,V>(t, f, 0, f, this);
     }
 
-    /* ---------------- Iterator Support -------------- */
-
-    abstract class HashIterator {
-        int nextSegmentIndex;
-        int nextTableIndex;
-        HashEntry<K,V>[] currentTable;
-        HashEntry<K, V> nextEntry;
-        HashEntry<K, V> lastReturned;
-
-        HashIterator() {
-            nextSegmentIndex = segments.length - 1;
-            nextTableIndex = -1;
-            advance();
+    /**
+     * Returns the hash code value for this {@link Map}, i.e.,
+     * the sum of, for each key-value pair in the map,
+     * {@code key.hashCode() ^ value.hashCode()}.
+     *
+     * @return the hash code value for this map
+     */
+    public int hashCode() {
+        int h = 0;
+        Node<K,V>[] t;
+        if ((t = table) != null) {
+            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+            for (Node<K,V> p; (p = it.advance()) != null; )
+                h += p.key.hashCode() ^ p.val.hashCode();
         }
-
-        /**
-         * Sets nextEntry to first node of next non-empty table
-         * (in backwards order, to simplify checks).
-         */
-        final void advance() {
+        return h;
+    }
+
+    /**
+     * Returns a string representation of this map.  The string
+     * representation consists of a list of key-value mappings (in no
+     * particular order) enclosed in braces ("{@code {}}").  Adjacent
+     * mappings are separated by the characters {@code ", "} (comma
+     * and space).  Each key-value mapping is rendered as the key
+     * followed by an equals sign ("{@code =}") followed by the
+     * associated value.
+     *
+     * @return a string representation of this map
+     */
+    public String toString() {
+        Node<K,V>[] t;
+        int f = (t = table) == null ? 0 : t.length;
+        Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f);
+        StringBuilder sb = new StringBuilder();
+        sb.append('{');
+        Node<K,V> p;
+        if ((p = it.advance()) != null) {
             for (;;) {
-                if (nextTableIndex >= 0) {
-                    if ((nextEntry = entryAt(currentTable,
-                                             nextTableIndex--)) != null)
-                        break;
-                }
-                else if (nextSegmentIndex >= 0) {
-                    Segment<K,V> seg = segmentAt(segments, nextSegmentIndex--);
-                    if (seg != null && (currentTable = seg.table) != null)
-                        nextTableIndex = currentTable.length - 1;
-                }
-                else
+                K k = (K)p.key;
+                V v = p.val;
+                sb.append(k == this ? "(this Map)" : k);
+                sb.append('=');
+                sb.append(v == this ? "(this Map)" : v);
+                if ((p = it.advance()) == null)
                     break;
+                sb.append(',').append(' ');
             }
         }
-
-        final HashEntry<K,V> nextEntry() {
-            HashEntry<K,V> e = nextEntry;
-            if (e == null)
-                throw new NoSuchElementException();
-            lastReturned = e; // cannot assign until after null check
-            if ((nextEntry = e.next) == null)
-                advance();
-            return e;
+        return sb.append('}').toString();
+    }
+
+    /**
+     * Compares the specified object with this map for equality.
+     * Returns {@code true} if the given object is a map with the same
+     * mappings as this map.  This operation may return misleading
+     * results if either map is concurrently modified during execution
+     * of this method.
+     *
+     * @param o object to be compared for equality with this map
+     * @return {@code true} if the specified object is equal to this map
+     */
+    public boolean equals(Object o) {
+        if (o != this) {
+            if (!(o instanceof Map))
+                return false;
+            Map<?,?> m = (Map<?,?>) o;
+            Node<K,V>[] t;
+            int f = (t = table) == null ? 0 : t.length;
+            Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f);
+            for (Node<K,V> p; (p = it.advance()) != null; ) {
+                V val = p.val;
+                Object v = m.get(p.key);
+                if (v == null || (v != val && !v.equals(val)))
+                    return false;
+            }
+            for (Map.Entry<?,?> e : m.entrySet()) {
+                Object mk, mv, v;
+                if ((mk = e.getKey()) == null ||
+                    (mv = e.getValue()) == null ||
+                    (v = internalGet(mk)) == null ||
+                    (mv != v && !mv.equals(v)))
+                    return false;
+            }
         }
-
-        public final boolean hasNext() { return nextEntry != null; }
-        public final boolean hasMoreElements() { return nextEntry != null; }
-
-        public final void remove() {
-            if (lastReturned == null)
-                throw new IllegalStateException();
-            ConcurrentHashMap.this.remove(lastReturned.key);
-            lastReturned = null;
-        }
+        return true;
     }
 
-    final class KeyIterator
-        extends HashIterator
-        implements Iterator<K>, Enumeration<K>
-    {
-        public final K next()        { return super.nextEntry().key; }
-        public final K nextElement() { return super.nextEntry().key; }
+    /* ---------------- Serialization Support -------------- */
+
+    /**
+     * Stripped-down version of helper class used in previous version,
+     * declared for the sake of serialization compatibility
+     */
+    static class Segment<K,V> extends ReentrantLock implements Serializable {
+        private static final long serialVersionUID = 2249069246763182397L;
+        final float loadFactor;
+        Segment(float lf) { this.loadFactor = lf; }
     }
 
-    final class ValueIterator
-        extends HashIterator
-        implements Iterator<V>, Enumeration<V>
-    {
-        public final V next()        { return super.nextEntry().value; }
-        public final V nextElement() { return super.nextEntry().value; }
-    }
-
-    /**
-     * Custom Entry class used by EntryIterator.next(), that relays
-     * setValue changes to the underlying map.
-     */
-    final class WriteThroughEntry
-        extends AbstractMap.SimpleEntry<K,V>
-    {
-        static final long serialVersionUID = 7249069246763182397L;
-
-        WriteThroughEntry(K k, V v) {
-            super(k,v);
-        }
-
-        /**
-         * Sets our entry's value and writes through to the map. The
-         * value to return is somewhat arbitrary here. Since a
-         * WriteThroughEntry does not necessarily track asynchronous
-         * changes, the most recent "previous" value could be
-         * different from what we return (or could even have been
-         * removed in which case the put will re-establish). We do not
-         * and cannot guarantee more.
-         */
-        public V setValue(V value) {
-            if (value == null) throw new NullPointerException();
-            V v = super.setValue(value);
-            ConcurrentHashMap.this.put(getKey(), value);
-            return v;
-        }
-    }
-
-    final class EntryIterator
-        extends HashIterator
-        implements Iterator<Entry<K,V>>
-    {
-        public Map.Entry<K,V> next() {
-            HashEntry<K,V> e = super.nextEntry();
-            return new WriteThroughEntry(e.key, e.value);
-        }
-    }
-
-    final class KeySet extends AbstractSet<K> {
-        public Iterator<K> iterator() {
-            return new KeyIterator();
-        }
-        public int size() {
-            return ConcurrentHashMap.this.size();
-        }
-        public boolean isEmpty() {
-            return ConcurrentHashMap.this.isEmpty();
-        }
-        public boolean contains(Object o) {
-            return ConcurrentHashMap.this.containsKey(o);
-        }
-        public boolean remove(Object o) {
-            return ConcurrentHashMap.this.remove(o) != null;
-        }
-        public void clear() {
-            ConcurrentHashMap.this.clear();
-        }
-    }
-
-    final class Values extends AbstractCollection<V> {
-        public Iterator<V> iterator() {
-            return new ValueIterator();
-        }
-        public int size() {
-            return ConcurrentHashMap.this.size();
-        }
-        public boolean isEmpty() {
-            return ConcurrentHashMap.this.isEmpty();
-        }
-        public boolean contains(Object o) {
-            return ConcurrentHashMap.this.containsValue(o);
-        }
-        public void clear() {
-            ConcurrentHashMap.this.clear();
-        }
-    }
-
-    final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
-        public Iterator<Map.Entry<K,V>> iterator() {
-            return new EntryIterator();
-        }
-        public boolean contains(Object o) {
-            if (!(o instanceof Map.Entry))
-                return false;
-            Map.Entry<?,?> e = (Map.Entry<?,?>)o;
-            V v = ConcurrentHashMap.this.get(e.getKey());
-            return v != null && v.equals(e.getValue());
-        }
-        public boolean remove(Object o) {
-            if (!(o instanceof Map.Entry))
-                return false;
-            Map.Entry<?,?> e = (Map.Entry<?,?>)o;
-            return ConcurrentHashMap.this.remove(e.getKey(), e.getValue());
-        }
-        public int size() {
-            return ConcurrentHashMap.this.size();
-        }
-        public boolean isEmpty() {
-            return ConcurrentHashMap.this.isEmpty();
-        }
-        public void clear() {
-            ConcurrentHashMap.this.clear();
-        }
-    }
-
-    /* ---------------- Serialization Support -------------- */
-
     /**
      * Saves the state of the {@code ConcurrentHashMap} instance to a
      * stream (i.e., serializes it).
@@ -1448,119 +3166,2701 @@
      * The key-value mappings are emitted in no particular order.
      */
     private void writeObject(java.io.ObjectOutputStream s)
-            throws java.io.IOException {
-        // force all segments for serialization compatibility
-        for (int k = 0; k < segments.length; ++k)
-            ensureSegment(k);
-        s.defaultWriteObject();
-
-        final Segment<K,V>[] segments = this.segments;
-        for (int k = 0; k < segments.length; ++k) {
-            Segment<K,V> seg = segmentAt(segments, k);
-            seg.lock();
-            try {
-                HashEntry<K,V>[] tab = seg.table;
-                for (int i = 0; i < tab.length; ++i) {
-                    HashEntry<K,V> e;
-                    for (e = entryAt(tab, i); e != null; e = e.next) {
-                        s.writeObject(e.key);
-                        s.writeObject(e.value);
-                    }
-                }
-            } finally {
-                seg.unlock();
+        throws java.io.IOException {
+        // For serialization compatibility
+        // Emulate segment calculation from previous version of this class
+        int sshift = 0;
+        int ssize = 1;
+        while (ssize < DEFAULT_CONCURRENCY_LEVEL) {
+            ++sshift;
+            ssize <<= 1;
+        }
+        int segmentShift = 32 - sshift;
+        int segmentMask = ssize - 1;
+        Segment<K,V>[] segments = (Segment<K,V>[])
+            new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
+        for (int i = 0; i < segments.length; ++i)
+            segments[i] = new Segment<K,V>(LOAD_FACTOR);
+        s.putFields().put("segments", segments);
+        s.putFields().put("segmentShift", segmentShift);
+        s.putFields().put("segmentMask", segmentMask);
+        s.writeFields();
+
+        Node<K,V>[] t;
+        if ((t = table) != null) {
+            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+            for (Node<K,V> p; (p = it.advance()) != null; ) {
+                s.writeObject(p.key);
+                s.writeObject(p.val);
             }
         }
         s.writeObject(null);
         s.writeObject(null);
+        segments = null; // throw away
     }
 
     /**
      * Reconstitutes the instance from a stream (that is, deserializes it).
      * @param s the stream
      */
-    @SuppressWarnings("unchecked")
     private void readObject(java.io.ObjectInputStream s)
-            throws java.io.IOException, ClassNotFoundException {
-        // Don't call defaultReadObject()
-        ObjectInputStream.GetField oisFields = s.readFields();
-        final Segment<K,V>[] oisSegments = (Segment<K,V>[])oisFields.get("segments", null);
-
-        final int ssize = oisSegments.length;
-        if (ssize < 1 || ssize > MAX_SEGMENTS
-            || (ssize & (ssize-1)) != 0 )  // ssize not power of two
-            throw new java.io.InvalidObjectException("Bad number of segments:"
-                                                     + ssize);
-        int sshift = 0, ssizeTmp = ssize;
-        while (ssizeTmp > 1) {
-            ++sshift;
-            ssizeTmp >>>= 1;
+        throws java.io.IOException, ClassNotFoundException {
+        s.defaultReadObject();
+
+        // Create all nodes, then place in table once size is known
+        long size = 0L;
+        Node<K,V> p = null;
+        for (;;) {
+            K k = (K) s.readObject();
+            V v = (V) s.readObject();
+            if (k != null && v != null) {
+                int h = spread(k.hashCode());
+                p = new Node<K,V>(h, k, v, p);
+                ++size;
+            }
+            else
+                break;
         }
-        UNSAFE.putIntVolatile(this, SEGSHIFT_OFFSET, 32 - sshift);
-        UNSAFE.putIntVolatile(this, SEGMASK_OFFSET, ssize - 1);
-        UNSAFE.putObjectVolatile(this, SEGMENTS_OFFSET, oisSegments);
-
-        // set hashMask
-        UNSAFE.putIntVolatile(this, HASHSEED_OFFSET,
-                 sun.misc.Hashing.randomHashSeed(this));
-
-        // Re-initialize segments to be minimally sized, and let grow.
-        int cap = MIN_SEGMENT_TABLE_CAPACITY;
-        final Segment<K,V>[] segments = this.segments;
-        for (int k = 0; k < segments.length; ++k) {
-            Segment<K,V> seg = segments[k];
-            if (seg != null) {
-                seg.threshold = (int)(cap * seg.loadFactor);
-                seg.table = (HashEntry<K,V>[]) new HashEntry<?,?>[cap];
+        if (p != null) {
+            boolean init = false;
+            int n;
+            if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
+                n = MAXIMUM_CAPACITY;
+            else {
+                int sz = (int)size;
+                n = tableSizeFor(sz + (sz >>> 1) + 1);
+            }
+            int sc = sizeCtl;
+            boolean collide = false;
+            if (n > sc &&
+                U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
+                try {
+                    if (table == null) {
+                        init = true;
+                        Node<K,V>[] tab = (Node<K,V>[])new Node[n];
+                        int mask = n - 1;
+                        while (p != null) {
+                            int j = p.hash & mask;
+                            Node<K,V> next = p.next;
+                            Node<K,V> q = p.next = tabAt(tab, j);
+                            setTabAt(tab, j, p);
+                            if (!collide && q != null && q.hash == p.hash)
+                                collide = true;
+                            p = next;
+                        }
+                        table = tab;
+                        addCount(size, -1);
+                        sc = n - (n >>> 2);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+                if (collide) { // rescan and convert to TreeBins
+                    Node<K,V>[] tab = table;
+                    for (int i = 0; i < tab.length; ++i) {
+                        int c = 0;
+                        for (Node<K,V> e = tabAt(tab, i); e != null; e = e.next) {
+                            if (++c > TREE_THRESHOLD &&
+                                (e.key instanceof Comparable)) {
+                                replaceWithTreeBin(tab, i, e.key);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+            if (!init) { // Can only happen if unsafely published.
+                while (p != null) {
+                    internalPut((K)p.key, p.val, false);
+                    p = p.next;
+                }
             }
         }
-
-        // Read the keys and values, and put the mappings in the table
-        for (;;) {
-            K key = (K) s.readObject();
-            V value = (V) s.readObject();
-            if (key == null)
-                break;
-            put(key, value);
+    }
+
+    // -------------------------------------------------------
+
+    // Overrides of other default Map methods
+
+    public void forEach(BiConsumer<? super K, ? super V> action) {
+        if (action == null) throw new NullPointerException();
+        Node<K,V>[] t;
+        if ((t = table) != null) {
+            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+            for (Node<K,V> p; (p = it.advance()) != null; ) {
+                action.accept((K)p.key, p.val);
+            }
         }
     }
 
+    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        if (function == null) throw new NullPointerException();
+        Node<K,V>[] t;
+        if ((t = table) != null) {
+            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+            for (Node<K,V> p; (p = it.advance()) != null; ) {
+                K k = (K)p.key;
+                internalPut(k, function.apply(k, p.val), false);
+            }
+        }
+    }
+
+    // -------------------------------------------------------
+
+    // Parallel bulk operations
+
+    /**
+     * Computes initial batch value for bulk tasks. The returned value
+     * is approximately exp2 of the number of times (minus one) to
+     * split task by two before executing leaf action. This value is
+     * faster to compute and more convenient to use as a guide to
+     * splitting than is the depth, since it is used while dividing by
+     * two anyway.
+     */
+    final int batchFor(long b) {
+        long n;
+        if (b == Long.MAX_VALUE || (n = sumCount()) <= 1L || n < b)
+            return 0;
+        int sp = ForkJoinPool.getCommonPoolParallelism() << 2; // slack of 4
+        return (b <= 0L || (n /= b) >= sp) ? sp : (int)n;
+    }
+
+    /**
+     * Performs the given action for each (key, value).
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param action the action
+     */
+    public void forEach(long parallelismThreshold,
+                        BiConsumer<? super K,? super V> action) {
+        if (action == null) throw new NullPointerException();
+        new ForEachMappingTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             action).invoke();
+    }
+
+    /**
+     * Performs the given action for each non-null transformation
+     * of each (key, value).
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case the action is not applied)
+     * @param action the action
+     */
+    public <U> void forEach(long parallelismThreshold,
+                            BiFunction<? super K, ? super V, ? extends U> transformer,
+                            Consumer<? super U> action) {
+        if (transformer == null || action == null)
+            throw new NullPointerException();
+        new ForEachTransformedMappingTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             transformer, action).invoke();
+    }
+
+    /**
+     * Returns a non-null result from applying the given search
+     * function on each (key, value), or null if none.  Upon
+     * success, further element processing is suppressed and the
+     * results of any other parallel invocations of the search
+     * function are ignored.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param searchFunction a function returning a non-null
+     * result on success, else null
+     * @return a non-null result from applying the given search
+     * function on each (key, value), or null if none
+     */
+    public <U> U search(long parallelismThreshold,
+                        BiFunction<? super K, ? super V, ? extends U> searchFunction) {
+        if (searchFunction == null) throw new NullPointerException();
+        return new SearchMappingsTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             searchFunction, new AtomicReference<U>()).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all (key, value) pairs using the given reducer to
+     * combine values, or null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case it is not combined)
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all (key, value) pairs
+     */
+    public <U> U reduce(long parallelismThreshold,
+                        BiFunction<? super K, ? super V, ? extends U> transformer,
+                        BiFunction<? super U, ? super U, ? extends U> reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceMappingsTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all (key, value) pairs using the given reducer to
+     * combine values, and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all (key, value) pairs
+     */
+    public double reduceToDoubleIn(long parallelismThreshold,
+                                   ToDoubleBiFunction<? super K, ? super V> transformer,
+                                   double basis,
+                                   DoubleBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceMappingsToDoubleTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all (key, value) pairs using the given reducer to
+     * combine values, and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all (key, value) pairs
+     */
+    public long reduceToLong(long parallelismThreshold,
+                             ToLongBiFunction<? super K, ? super V> transformer,
+                             long basis,
+                             LongBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceMappingsToLongTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all (key, value) pairs using the given reducer to
+     * combine values, and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all (key, value) pairs
+     */
+    public int reduceToInt(long parallelismThreshold,
+                           ToIntBiFunction<? super K, ? super V> transformer,
+                           int basis,
+                           IntBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceMappingsToIntTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Performs the given action for each key.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param action the action
+     */
+    public void forEachKey(long parallelismThreshold,
+                           Consumer<? super K> action) {
+        if (action == null) throw new NullPointerException();
+        new ForEachKeyTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             action).invoke();
+    }
+
+    /**
+     * Performs the given action for each non-null transformation
+     * of each key.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case the action is not applied)
+     * @param action the action
+     */
+    public <U> void forEachKey(long parallelismThreshold,
+                               Function<? super K, ? extends U> transformer,
+                               Consumer<? super U> action) {
+        if (transformer == null || action == null)
+            throw new NullPointerException();
+        new ForEachTransformedKeyTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             transformer, action).invoke();
+    }
+
+    /**
+     * Returns a non-null result from applying the given search
+     * function on each key, or null if none. Upon success,
+     * further element processing is suppressed and the results of
+     * any other parallel invocations of the search function are
+     * ignored.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param searchFunction a function returning a non-null
+     * result on success, else null
+     * @return a non-null result from applying the given search
+     * function on each key, or null if none
+     */
+    public <U> U searchKeys(long parallelismThreshold,
+                            Function<? super K, ? extends U> searchFunction) {
+        if (searchFunction == null) throw new NullPointerException();
+        return new SearchKeysTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             searchFunction, new AtomicReference<U>()).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating all keys using the given
+     * reducer to combine values, or null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating all keys using the given
+     * reducer to combine values, or null if none
+     */
+    public K reduceKeys(long parallelismThreshold,
+                        BiFunction<? super K, ? super K, ? extends K> reducer) {
+        if (reducer == null) throw new NullPointerException();
+        return new ReduceKeysTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all keys using the given reducer to combine values, or
+     * null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case it is not combined)
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all keys
+     */
+    public <U> U reduceKeys(long parallelismThreshold,
+                            Function<? super K, ? extends U> transformer,
+         BiFunction<? super U, ? super U, ? extends U> reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceKeysTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all keys using the given reducer to combine values, and
+     * the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all keys
+     */
+    public double reduceKeysToDouble(long parallelismThreshold,
+                                     ToDoubleFunction<? super K> transformer,
+                                     double basis,
+                                     DoubleBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceKeysToDoubleTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all keys using the given reducer to combine values, and
+     * the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all keys
+     */
+    public long reduceKeysToLong(long parallelismThreshold,
+                                 ToLongFunction<? super K> transformer,
+                                 long basis,
+                                 LongBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceKeysToLongTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all keys using the given reducer to combine values, and
+     * the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all keys
+     */
+    public int reduceKeysToInt(long parallelismThreshold,
+                               ToIntFunction<? super K> transformer,
+                               int basis,
+                               IntBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceKeysToIntTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Performs the given action for each value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param action the action
+     */
+    public void forEachValue(long parallelismThreshold,
+                             Consumer<? super V> action) {
+        if (action == null)
+            throw new NullPointerException();
+        new ForEachValueTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             action).invoke();
+    }
+
+    /**
+     * Performs the given action for each non-null transformation
+     * of each value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case the action is not applied)
+     * @param action the action
+     */
+    public <U> void forEachValue(long parallelismThreshold,
+                                 Function<? super V, ? extends U> transformer,
+                                 Consumer<? super U> action) {
+        if (transformer == null || action == null)
+            throw new NullPointerException();
+        new ForEachTransformedValueTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             transformer, action).invoke();
+    }
+
+    /**
+     * Returns a non-null result from applying the given search
+     * function on each value, or null if none.  Upon success,
+     * further element processing is suppressed and the results of
+     * any other parallel invocations of the search function are
+     * ignored.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param searchFunction a function returning a non-null
+     * result on success, else null
+     * @return a non-null result from applying the given search
+     * function on each value, or null if none
+     */
+    public <U> U searchValues(long parallelismThreshold,
+                              Function<? super V, ? extends U> searchFunction) {
+        if (searchFunction == null) throw new NullPointerException();
+        return new SearchValuesTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             searchFunction, new AtomicReference<U>()).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating all values using the
+     * given reducer to combine values, or null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating all values
+     */
+    public V reduceValues(long parallelismThreshold,
+                          BiFunction<? super V, ? super V, ? extends V> reducer) {
+        if (reducer == null) throw new NullPointerException();
+        return new ReduceValuesTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all values using the given reducer to combine values, or
+     * null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case it is not combined)
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all values
+     */
+    public <U> U reduceValues(long parallelismThreshold,
+                              Function<? super V, ? extends U> transformer,
+                              BiFunction<? super U, ? super U, ? extends U> reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceValuesTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all values using the given reducer to combine values,
+     * and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all values
+     */
+    public double reduceValuesToDouble(long parallelismThreshold,
+                                       ToDoubleFunction<? super V> transformer,
+                                       double basis,
+                                       DoubleBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceValuesToDoubleTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all values using the given reducer to combine values,
+     * and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all values
+     */
+    public long reduceValuesToLong(long parallelismThreshold,
+                                   ToLongFunction<? super V> transformer,
+                                   long basis,
+                                   LongBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceValuesToLongTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all values using the given reducer to combine values,
+     * and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all values
+     */
+    public int reduceValuesToInt(long parallelismThreshold,
+                                 ToIntFunction<? super V> transformer,
+                                 int basis,
+                                 IntBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceValuesToIntTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Performs the given action for each entry.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param action the action
+     */
+    public void forEachEntry(long parallelismThreshold,
+                             Consumer<? super Map.Entry<K,V>> action) {
+        if (action == null) throw new NullPointerException();
+        new ForEachEntryTask<K,V>(null, batchFor(parallelismThreshold), 0, 0, table,
+                                  action).invoke();
+    }
+
+    /**
+     * Performs the given action for each non-null transformation
+     * of each entry.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case the action is not applied)
+     * @param action the action
+     */
+    public <U> void forEachEntry(long parallelismThreshold,
+                                 Function<Map.Entry<K,V>, ? extends U> transformer,
+                                 Consumer<? super U> action) {
+        if (transformer == null || action == null)
+            throw new NullPointerException();
+        new ForEachTransformedEntryTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             transformer, action).invoke();
+    }
+
+    /**
+     * Returns a non-null result from applying the given search
+     * function on each entry, or null if none.  Upon success,
+     * further element processing is suppressed and the results of
+     * any other parallel invocations of the search function are
+     * ignored.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param searchFunction a function returning a non-null
+     * result on success, else null
+     * @return a non-null result from applying the given search
+     * function on each entry, or null if none
+     */
+    public <U> U searchEntries(long parallelismThreshold,
+                               Function<Map.Entry<K,V>, ? extends U> searchFunction) {
+        if (searchFunction == null) throw new NullPointerException();
+        return new SearchEntriesTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             searchFunction, new AtomicReference<U>()).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating all entries using the
+     * given reducer to combine values, or null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating all entries
+     */
+    public Map.Entry<K,V> reduceEntries(long parallelismThreshold,
+                                        BiFunction<Map.Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer) {
+        if (reducer == null) throw new NullPointerException();
+        return new ReduceEntriesTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all entries using the given reducer to combine values,
+     * or null if none.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element, or null if there is no transformation (in
+     * which case it is not combined)
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all entries
+     */
+    public <U> U reduceEntries(long parallelismThreshold,
+                               Function<Map.Entry<K,V>, ? extends U> transformer,
+                               BiFunction<? super U, ? super U, ? extends U> reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceEntriesTask<K,V,U>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all entries using the given reducer to combine values,
+     * and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all entries
+     */
+    public double reduceEntriesToDouble(long parallelismThreshold,
+                                        ToDoubleFunction<Map.Entry<K,V>> transformer,
+                                        double basis,
+                                        DoubleBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceEntriesToDoubleTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all entries using the given reducer to combine values,
+     * and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all entries
+     */
+    public long reduceEntriesToLong(long parallelismThreshold,
+                                    ToLongFunction<Map.Entry<K,V>> transformer,
+                                    long basis,
+                                    LongBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceEntriesToLongTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+    /**
+     * Returns the result of accumulating the given transformation
+     * of all entries using the given reducer to combine values,
+     * and the given basis as an identity value.
+     *
+     * @param parallelismThreshold the (estimated) number of elements
+     * needed for this operation to be executed in parallel
+     * @param transformer a function returning the transformation
+     * for an element
+     * @param basis the identity (initial default value) for the reduction
+     * @param reducer a commutative associative combining function
+     * @return the result of accumulating the given transformation
+     * of all entries
+     */
+    public int reduceEntriesToInt(long parallelismThreshold,
+                                  ToIntFunction<Map.Entry<K,V>> transformer,
+                                  int basis,
+                                  IntBinaryOperator reducer) {
+        if (transformer == null || reducer == null)
+            throw new NullPointerException();
+        return new MapReduceEntriesToIntTask<K,V>
+            (null, batchFor(parallelismThreshold), 0, 0, table,
+             null, transformer, basis, reducer).invoke();
+    }
+
+
+    /* ----------------Views -------------- */
+
+    /**
+     * Base class for views.
+     */
+    abstract static class CollectionView<K,V,E>
+        implements Collection<E>, java.io.Serializable {
+        private static final long serialVersionUID = 7249069246763182397L;
+        final ConcurrentHashMap<K,V> map;
+        CollectionView(ConcurrentHashMap<K,V> map)  { this.map = map; }
+
+        /**
+         * Returns the map backing this view.
+         *
+         * @return the map backing this view
+         */
+        public ConcurrentHashMap<K,V> getMap() { return map; }
+
+        /**
+         * Removes all of the elements from this view, by removing all
+         * the mappings from the map backing this view.
+         */
+        public final void clear()      { map.clear(); }
+        public final int size()        { return map.size(); }
+        public final boolean isEmpty() { return map.isEmpty(); }
+
+        // implementations below rely on concrete classes supplying these
+        // abstract methods
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         */
+        public abstract Iterator<E> iterator();
+        public abstract boolean contains(Object o);
+        public abstract boolean remove(Object o);
+
+        private static final String oomeMsg = "Required array size too large";
+
+        public final Object[] toArray() {
+            long sz = map.mappingCount();
+            if (sz > MAX_ARRAY_SIZE)
+                throw new OutOfMemoryError(oomeMsg);
+            int n = (int)sz;
+            Object[] r = new Object[n];
+            int i = 0;
+            for (E e : this) {
+                if (i == n) {
+                    if (n >= MAX_ARRAY_SIZE)
+                        throw new OutOfMemoryError(oomeMsg);
+                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
+                        n = MAX_ARRAY_SIZE;
+                    else
+                        n += (n >>> 1) + 1;
+                    r = Arrays.copyOf(r, n);
+                }
+                r[i++] = e;
+            }
+            return (i == n) ? r : Arrays.copyOf(r, i);
+        }
+
+        public final <T> T[] toArray(T[] a) {
+            long sz = map.mappingCount();
+            if (sz > MAX_ARRAY_SIZE)
+                throw new OutOfMemoryError(oomeMsg);
+            int m = (int)sz;
+            T[] r = (a.length >= m) ? a :
+                (T[])java.lang.reflect.Array
+                .newInstance(a.getClass().getComponentType(), m);
+            int n = r.length;
+            int i = 0;
+            for (E e : this) {
+                if (i == n) {
+                    if (n >= MAX_ARRAY_SIZE)
+                        throw new OutOfMemoryError(oomeMsg);
+                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
+                        n = MAX_ARRAY_SIZE;
+                    else
+                        n += (n >>> 1) + 1;
+                    r = Arrays.copyOf(r, n);
+                }
+                r[i++] = (T)e;
+            }
+            if (a == r && i < n) {
+                r[i] = null; // null-terminate
+                return r;
+            }
+            return (i == n) ? r : Arrays.copyOf(r, i);
+        }
+
+        /**
+         * Returns a string representation of this collection.
+         * The string representation consists of the string representations
+         * of the collection's elements in the order they are returned by
+         * its iterator, enclosed in square brackets ({@code "[]"}).
+         * Adjacent elements are separated by the characters {@code ", "}
+         * (comma and space).  Elements are converted to strings as by
+         * {@link String#valueOf(Object)}.
+         *
+         * @return a string representation of this collection
+         */
+        public final String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append('[');
+            Iterator<E> it = iterator();
+            if (it.hasNext()) {
+                for (;;) {
+                    Object e = it.next();
+                    sb.append(e == this ? "(this Collection)" : e);
+                    if (!it.hasNext())
+                        break;
+                    sb.append(',').append(' ');
+                }
+            }
+            return sb.append(']').toString();
+        }
+
+        public final boolean containsAll(Collection<?> c) {
+            if (c != this) {
+                for (Object e : c) {
+                    if (e == null || !contains(e))
+                        return false;
+                }
+            }
+            return true;
+        }
+
+        public final boolean removeAll(Collection<?> c) {
+            boolean modified = false;
+            for (Iterator<E> it = iterator(); it.hasNext();) {
+                if (c.contains(it.next())) {
+                    it.remove();
+                    modified = true;
+                }
+            }
+            return modified;
+        }
+
+        public final boolean retainAll(Collection<?> c) {
+            boolean modified = false;
+            for (Iterator<E> it = iterator(); it.hasNext();) {
+                if (!c.contains(it.next())) {
+                    it.remove();
+                    modified = true;
+                }
+            }
+            return modified;
+        }
+
+    }
+
+    /**
+     * A view of a ConcurrentHashMap as a {@link Set} of keys, in
+     * which additions may optionally be enabled by mapping to a
+     * common value.  This class cannot be directly instantiated.
+     * See {@link #keySet() keySet()},
+     * {@link #keySet(Object) keySet(V)},
+     * {@link #newKeySet() newKeySet()},
+     * {@link #newKeySet(int) newKeySet(int)}.
+     */
+    public static class KeySetView<K,V> extends CollectionView<K,V,K>
+        implements Set<K>, java.io.Serializable {
+        private static final long serialVersionUID = 7249069246763182397L;
+        private final V value;
+        KeySetView(ConcurrentHashMap<K,V> map, V value) {  // non-public
+            super(map);
+            this.value = value;
+        }
+
+        /**
+         * Returns the default mapped value for additions,
+         * or {@code null} if additions are not supported.
+         *
+         * @return the default mapped value for additions, or {@code null}
+         * if not supported
+         */
+        public V getMappedValue() { return value; }
+
+        /**
+         * {@inheritDoc}
+         * @throws NullPointerException if the specified key is null
+         */
+        public boolean contains(Object o) { return map.containsKey(o); }
+
+        /**
+         * Removes the key from this map view, by removing the key (and its
+         * corresponding value) from the backing map.  This method does
+         * nothing if the key is not in the map.
+         *
+         * @param  o the key to be removed from the backing map
+         * @return {@code true} if the backing map contained the specified key
+         * @throws NullPointerException if the specified key is null
+         */
+        public boolean remove(Object o) { return map.remove(o) != null; }
+
+        /**
+         * @return an iterator over the keys of the backing map
+         */
+        public Iterator<K> iterator() {
+            Node<K,V>[] t;
+            ConcurrentHashMap<K,V> m = map;
+            int f = (t = m.table) == null ? 0 : t.length;
+            return new KeyIterator<K,V>(t, f, 0, f, m);
+        }
+
+        /**
+         * Adds the specified key to this set view by mapping the key to
+         * the default mapped value in the backing map, if defined.
+         *
+         * @param e key to be added
+         * @return {@code true} if this set changed as a result of the call
+         * @throws NullPointerException if the specified key is null
+         * @throws UnsupportedOperationException if no default mapped value
+         * for additions was provided
+         */
+        public boolean add(K e) {
+            V v;
+            if ((v = value) == null)
+                throw new UnsupportedOperationException();
+            return map.internalPut(e, v, true) == null;
+        }
+
+        /**
+         * Adds all of the elements in the specified collection to this set,
+         * as if by calling {@link #add} on each one.
+         *
+         * @param c the elements to be inserted into this set
+         * @return {@code true} if this set changed as a result of the call
+         * @throws NullPointerException if the collection or any of its
+         * elements are {@code null}
+         * @throws UnsupportedOperationException if no default mapped value
+         * for additions was provided
+         */
+        public boolean addAll(Collection<? extends K> c) {
+            boolean added = false;
+            V v;
+            if ((v = value) == null)
+                throw new UnsupportedOperationException();
+            for (K e : c) {
+                if (map.internalPut(e, v, true) == null)
+                    added = true;
+            }
+            return added;
+        }
+
+        public int hashCode() {
+            int h = 0;
+            for (K e : this)
+                h += e.hashCode();
+            return h;
+        }
+
+        public boolean equals(Object o) {
+            Set<?> c;
+            return ((o instanceof Set) &&
+                    ((c = (Set<?>)o) == this ||
+                     (containsAll(c) && c.containsAll(this))));
+        }
+
+        public Spliterator<K> spliterator() {
+            Node<K,V>[] t;
+            ConcurrentHashMap<K,V> m = map;
+            long n = m.sumCount();
+            int f = (t = m.table) == null ? 0 : t.length;
+            return new KeySpliterator<K,V>(t, f, 0, f, n < 0L ? 0L : n);
+        }
+
+        public void forEach(Consumer<? super K> action) {
+            if (action == null) throw new NullPointerException();
+            Node<K,V>[] t;
+            if ((t = map.table) != null) {
+                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+                for (Node<K,V> p; (p = it.advance()) != null; )
+                    action.accept((K)p.key);
+            }
+        }
+    }
+
+    /**
+     * A view of a ConcurrentHashMap as a {@link Collection} of
+     * values, in which additions are disabled. This class cannot be
+     * directly instantiated. See {@link #values()}.
+     */
+    static final class ValuesView<K,V> extends CollectionView<K,V,V>
+        implements Collection<V>, java.io.Serializable {
+        private static final long serialVersionUID = 2249069246763182397L;
+        ValuesView(ConcurrentHashMap<K,V> map) { super(map); }
+        public final boolean contains(Object o) {
+            return map.containsValue(o);
+        }
+
+        public final boolean remove(Object o) {
+            if (o != null) {
+                for (Iterator<V> it = iterator(); it.hasNext();) {
+                    if (o.equals(it.next())) {
+                        it.remove();
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
+
+        public final Iterator<V> iterator() {
+            ConcurrentHashMap<K,V> m = map;
+            Node<K,V>[] t;
+            int f = (t = m.table) == null ? 0 : t.length;
+            return new ValueIterator<K,V>(t, f, 0, f, m);
+        }
+
+        public final boolean add(V e) {
+            throw new UnsupportedOperationException();
+        }
+        public final boolean addAll(Collection<? extends V> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        public Spliterator<V> spliterator() {
+            Node<K,V>[] t;
+            ConcurrentHashMap<K,V> m = map;
+            long n = m.sumCount();
+            int f = (t = m.table) == null ? 0 : t.length;
+            return new ValueSpliterator<K,V>(t, f, 0, f, n < 0L ? 0L : n);
+        }
+
+        public void forEach(Consumer<? super V> action) {
+            if (action == null) throw new NullPointerException();
+            Node<K,V>[] t;
+            if ((t = map.table) != null) {
+                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+                for (Node<K,V> p; (p = it.advance()) != null; )
+                    action.accept(p.val);
+            }
+        }
+    }
+
+    /**
+     * A view of a ConcurrentHashMap as a {@link Set} of (key, value)
+     * entries.  This class cannot be directly instantiated. See
+     * {@link #entrySet()}.
+     */
+    static final class EntrySetView<K,V> extends CollectionView<K,V,Map.Entry<K,V>>
+        implements Set<Map.Entry<K,V>>, java.io.Serializable {
+        private static final long serialVersionUID = 2249069246763182397L;
+        EntrySetView(ConcurrentHashMap<K,V> map) { super(map); }
+
+        public boolean contains(Object o) {
+            Object k, v, r; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (r = map.get(k)) != null &&
+                    (v = e.getValue()) != null &&
+                    (v == r || v.equals(r)));
+        }
+
+        public boolean remove(Object o) {
+            Object k, v; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    map.remove(k, v));
+        }
+
+        /**
+         * @return an iterator over the entries of the backing map
+         */
+        public Iterator<Map.Entry<K,V>> iterator() {
+            ConcurrentHashMap<K,V> m = map;
+            Node<K,V>[] t;
+            int f = (t = m.table) == null ? 0 : t.length;
+            return new EntryIterator<K,V>(t, f, 0, f, m);
+        }
+
+        public boolean add(Entry<K,V> e) {
+            return map.internalPut(e.getKey(), e.getValue(), false) == null;
+        }
+
+        public boolean addAll(Collection<? extends Entry<K,V>> c) {
+            boolean added = false;
+            for (Entry<K,V> e : c) {
+                if (add(e))
+                    added = true;
+            }
+            return added;
+        }
+
+        public final int hashCode() {
+            int h = 0;
+            Node<K,V>[] t;
+            if ((t = map.table) != null) {
+                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+                for (Node<K,V> p; (p = it.advance()) != null; ) {
+                    h += p.hashCode();
+                }
+            }
+            return h;
+        }
+
+        public final boolean equals(Object o) {
+            Set<?> c;
+            return ((o instanceof Set) &&
+                    ((c = (Set<?>)o) == this ||
+                     (containsAll(c) && c.containsAll(this))));
+        }
+
+        public Spliterator<Map.Entry<K,V>> spliterator() {
+            Node<K,V>[] t;
+            ConcurrentHashMap<K,V> m = map;
+            long n = m.sumCount();
+            int f = (t = m.table) == null ? 0 : t.length;
+            return new EntrySpliterator<K,V>(t, f, 0, f, n < 0L ? 0L : n, m);
+        }
+
+        public void forEach(Consumer<? super Map.Entry<K,V>> action) {
+            if (action == null) throw new NullPointerException();
+            Node<K,V>[] t;
+            if ((t = map.table) != null) {
+                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);
+                for (Node<K,V> p; (p = it.advance()) != null; )
+                    action.accept(new MapEntry<K,V>((K)p.key, p.val, map));
+            }
+        }
+
+    }
+
+    // -------------------------------------------------------
+
+    /**
+     * Base class for bulk tasks. Repeats some fields and code from
+     * class Traverser, because we need to subclass CountedCompleter.
+     */
+    abstract static class BulkTask<K,V,R> extends CountedCompleter<R> {
+        Node<K,V>[] tab;        // same as Traverser
+        Node<K,V> next;
+        int index;
+        int baseIndex;
+        int baseLimit;
+        final int baseSize;
+        int batch;              // split control
+
+        BulkTask(BulkTask<K,V,?> par, int b, int i, int f, Node<K,V>[] t) {
+            super(par);
+            this.batch = b;
+            this.index = this.baseIndex = i;
+            if ((this.tab = t) == null)
+                this.baseSize = this.baseLimit = 0;
+            else if (par == null)
+                this.baseSize = this.baseLimit = t.length;
+            else {
+                this.baseLimit = f;
+                this.baseSize = par.baseSize;
+            }
+        }
+
+        /**
+         * Same as Traverser version
+         */
+        final Node<K,V> advance() {
+            Node<K,V> e;
+            if ((e = next) != null)
+                e = e.next;
+            for (;;) {
+                Node<K,V>[] t; int i, n; Object ek;
+                if (e != null)
+                    return next = e;
+                if (baseIndex >= baseLimit || (t = tab) == null ||
+                    (n = t.length) <= (i = index) || i < 0)
+                    return next = null;
+                if ((e = tabAt(t, index)) != null && e.hash < 0) {
+                    if ((ek = e.key) instanceof TreeBin)
+                        e = ((TreeBin<K,V>)ek).first;
+                    else {
+                        tab = (Node<K,V>[])ek;
+                        e = null;
+                        continue;
+                    }
+                }
+                if ((index += baseSize) >= n)
+                    index = ++baseIndex;
+            }
+        }
+    }
+
+    /*
+     * Task classes. Coded in a regular but ugly format/style to
+     * simplify checks that each variant differs in the right way from
+     * others. The null screenings exist because compilers cannot tell
+     * that we've already null-checked task arguments, so we force
+     * simplest hoisted bypass to help avoid convoluted traps.
+     */
+
+    static final class ForEachKeyTask<K,V>
+        extends BulkTask<K,V,Void> {
+        final Consumer<? super K> action;
+        ForEachKeyTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Consumer<? super K> action) {
+            super(p, b, i, f, t);
+            this.action = action;
+        }
+        public final void compute() {
+            final Consumer<? super K> action;
+            if ((action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachKeyTask<K,V>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null;)
+                    action.accept((K)p.key);
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachValueTask<K,V>
+        extends BulkTask<K,V,Void> {
+        final Consumer<? super V> action;
+        ForEachValueTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Consumer<? super V> action) {
+            super(p, b, i, f, t);
+            this.action = action;
+        }
+        public final void compute() {
+            final Consumer<? super V> action;
+            if ((action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachValueTask<K,V>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null;)
+                    action.accept(p.val);
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachEntryTask<K,V>
+        extends BulkTask<K,V,Void> {
+        final Consumer<? super Entry<K,V>> action;
+        ForEachEntryTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Consumer<? super Entry<K,V>> action) {
+            super(p, b, i, f, t);
+            this.action = action;
+        }
+        public final void compute() {
+            final Consumer<? super Entry<K,V>> action;
+            if ((action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachEntryTask<K,V>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    action.accept(p);
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachMappingTask<K,V>
+        extends BulkTask<K,V,Void> {
+        final BiConsumer<? super K, ? super V> action;
+        ForEachMappingTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             BiConsumer<? super K,? super V> action) {
+            super(p, b, i, f, t);
+            this.action = action;
+        }
+        public final void compute() {
+            final BiConsumer<? super K, ? super V> action;
+            if ((action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachMappingTask<K,V>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    action.accept((K)p.key, p.val);
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachTransformedKeyTask<K,V,U>
+        extends BulkTask<K,V,Void> {
+        final Function<? super K, ? extends U> transformer;
+        final Consumer<? super U> action;
+        ForEachTransformedKeyTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Function<? super K, ? extends U> transformer, Consumer<? super U> action) {
+            super(p, b, i, f, t);
+            this.transformer = transformer; this.action = action;
+        }
+        public final void compute() {
+            final Function<? super K, ? extends U> transformer;
+            final Consumer<? super U> action;
+            if ((transformer = this.transformer) != null &&
+                (action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachTransformedKeyTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         transformer, action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply((K)p.key)) != null)
+                        action.accept(u);
+                }
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachTransformedValueTask<K,V,U>
+        extends BulkTask<K,V,Void> {
+        final Function<? super V, ? extends U> transformer;
+        final Consumer<? super U> action;
+        ForEachTransformedValueTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Function<? super V, ? extends U> transformer, Consumer<? super U> action) {
+            super(p, b, i, f, t);
+            this.transformer = transformer; this.action = action;
+        }
+        public final void compute() {
+            final Function<? super V, ? extends U> transformer;
+            final Consumer<? super U> action;
+            if ((transformer = this.transformer) != null &&
+                (action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachTransformedValueTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         transformer, action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply(p.val)) != null)
+                        action.accept(u);
+                }
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachTransformedEntryTask<K,V,U>
+        extends BulkTask<K,V,Void> {
+        final Function<Map.Entry<K,V>, ? extends U> transformer;
+        final Consumer<? super U> action;
+        ForEachTransformedEntryTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Function<Map.Entry<K,V>, ? extends U> transformer, Consumer<? super U> action) {
+            super(p, b, i, f, t);
+            this.transformer = transformer; this.action = action;
+        }
+        public final void compute() {
+            final Function<Map.Entry<K,V>, ? extends U> transformer;
+            final Consumer<? super U> action;
+            if ((transformer = this.transformer) != null &&
+                (action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachTransformedEntryTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         transformer, action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply(p)) != null)
+                        action.accept(u);
+                }
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class ForEachTransformedMappingTask<K,V,U>
+        extends BulkTask<K,V,Void> {
+        final BiFunction<? super K, ? super V, ? extends U> transformer;
+        final Consumer<? super U> action;
+        ForEachTransformedMappingTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             BiFunction<? super K, ? super V, ? extends U> transformer,
+             Consumer<? super U> action) {
+            super(p, b, i, f, t);
+            this.transformer = transformer; this.action = action;
+        }
+        public final void compute() {
+            final BiFunction<? super K, ? super V, ? extends U> transformer;
+            final Consumer<? super U> action;
+            if ((transformer = this.transformer) != null &&
+                (action = this.action) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    new ForEachTransformedMappingTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         transformer, action).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply((K)p.key, p.val)) != null)
+                        action.accept(u);
+                }
+                propagateCompletion();
+            }
+        }
+    }
+
+    static final class SearchKeysTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final Function<? super K, ? extends U> searchFunction;
+        final AtomicReference<U> result;
+        SearchKeysTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Function<? super K, ? extends U> searchFunction,
+             AtomicReference<U> result) {
+            super(p, b, i, f, t);
+            this.searchFunction = searchFunction; this.result = result;
+        }
+        public final U getRawResult() { return result.get(); }
+        public final void compute() {
+            final Function<? super K, ? extends U> searchFunction;
+            final AtomicReference<U> result;
+            if ((searchFunction = this.searchFunction) != null &&
+                (result = this.result) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    if (result.get() != null)
+                        return;
+                    addToPendingCount(1);
+                    new SearchKeysTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         searchFunction, result).fork();
+                }
+                while (result.get() == null) {
+                    U u;
+                    Node<K,V> p;
+                    if ((p = advance()) == null) {
+                        propagateCompletion();
+                        break;
+                    }
+                    if ((u = searchFunction.apply((K)p.key)) != null) {
+                        if (result.compareAndSet(null, u))
+                            quietlyCompleteRoot();
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class SearchValuesTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final Function<? super V, ? extends U> searchFunction;
+        final AtomicReference<U> result;
+        SearchValuesTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Function<? super V, ? extends U> searchFunction,
+             AtomicReference<U> result) {
+            super(p, b, i, f, t);
+            this.searchFunction = searchFunction; this.result = result;
+        }
+        public final U getRawResult() { return result.get(); }
+        public final void compute() {
+            final Function<? super V, ? extends U> searchFunction;
+            final AtomicReference<U> result;
+            if ((searchFunction = this.searchFunction) != null &&
+                (result = this.result) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    if (result.get() != null)
+                        return;
+                    addToPendingCount(1);
+                    new SearchValuesTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         searchFunction, result).fork();
+                }
+                while (result.get() == null) {
+                    U u;
+                    Node<K,V> p;
+                    if ((p = advance()) == null) {
+                        propagateCompletion();
+                        break;
+                    }
+                    if ((u = searchFunction.apply(p.val)) != null) {
+                        if (result.compareAndSet(null, u))
+                            quietlyCompleteRoot();
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class SearchEntriesTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final Function<Entry<K,V>, ? extends U> searchFunction;
+        final AtomicReference<U> result;
+        SearchEntriesTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             Function<Entry<K,V>, ? extends U> searchFunction,
+             AtomicReference<U> result) {
+            super(p, b, i, f, t);
+            this.searchFunction = searchFunction; this.result = result;
+        }
+        public final U getRawResult() { return result.get(); }
+        public final void compute() {
+            final Function<Entry<K,V>, ? extends U> searchFunction;
+            final AtomicReference<U> result;
+            if ((searchFunction = this.searchFunction) != null &&
+                (result = this.result) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    if (result.get() != null)
+                        return;
+                    addToPendingCount(1);
+                    new SearchEntriesTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         searchFunction, result).fork();
+                }
+                while (result.get() == null) {
+                    U u;
+                    Node<K,V> p;
+                    if ((p = advance()) == null) {
+                        propagateCompletion();
+                        break;
+                    }
+                    if ((u = searchFunction.apply(p)) != null) {
+                        if (result.compareAndSet(null, u))
+                            quietlyCompleteRoot();
+                        return;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class SearchMappingsTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final BiFunction<? super K, ? super V, ? extends U> searchFunction;
+        final AtomicReference<U> result;
+        SearchMappingsTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             BiFunction<? super K, ? super V, ? extends U> searchFunction,
+             AtomicReference<U> result) {
+            super(p, b, i, f, t);
+            this.searchFunction = searchFunction; this.result = result;
+        }
+        public final U getRawResult() { return result.get(); }
+        public final void compute() {
+            final BiFunction<? super K, ? super V, ? extends U> searchFunction;
+            final AtomicReference<U> result;
+            if ((searchFunction = this.searchFunction) != null &&
+                (result = this.result) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    if (result.get() != null)
+                        return;
+                    addToPendingCount(1);
+                    new SearchMappingsTask<K,V,U>
+                        (this, batch >>>= 1, baseLimit = h, f, tab,
+                         searchFunction, result).fork();
+                }
+                while (result.get() == null) {
+                    U u;
+                    Node<K,V> p;
+                    if ((p = advance()) == null) {
+                        propagateCompletion();
+                        break;
+                    }
+                    if ((u = searchFunction.apply((K)p.key, p.val)) != null) {
+                        if (result.compareAndSet(null, u))
+                            quietlyCompleteRoot();
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class ReduceKeysTask<K,V>
+        extends BulkTask<K,V,K> {
+        final BiFunction<? super K, ? super K, ? extends K> reducer;
+        K result;
+        ReduceKeysTask<K,V> rights, nextRight;
+        ReduceKeysTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             ReduceKeysTask<K,V> nextRight,
+             BiFunction<? super K, ? super K, ? extends K> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.reducer = reducer;
+        }
+        public final K getRawResult() { return result; }
+        public final void compute() {
+            final BiFunction<? super K, ? super K, ? extends K> reducer;
+            if ((reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new ReduceKeysTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, reducer)).fork();
+                }
+                K r = null;
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    K u = (K)p.key;
+                    r = (r == null) ? u : u == null ? r : reducer.apply(r, u);
+                }
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    ReduceKeysTask<K,V>
+                        t = (ReduceKeysTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        K tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class ReduceValuesTask<K,V>
+        extends BulkTask<K,V,V> {
+        final BiFunction<? super V, ? super V, ? extends V> reducer;
+        V result;
+        ReduceValuesTask<K,V> rights, nextRight;
+        ReduceValuesTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             ReduceValuesTask<K,V> nextRight,
+             BiFunction<? super V, ? super V, ? extends V> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.reducer = reducer;
+        }
+        public final V getRawResult() { return result; }
+        public final void compute() {
+            final BiFunction<? super V, ? super V, ? extends V> reducer;
+            if ((reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new ReduceValuesTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, reducer)).fork();
+                }
+                V r = null;
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    V v = p.val;
+                    r = (r == null) ? v : reducer.apply(r, v);
+                }
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    ReduceValuesTask<K,V>
+                        t = (ReduceValuesTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        V tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class ReduceEntriesTask<K,V>
+        extends BulkTask<K,V,Map.Entry<K,V>> {
+        final BiFunction<Map.Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer;
+        Map.Entry<K,V> result;
+        ReduceEntriesTask<K,V> rights, nextRight;
+        ReduceEntriesTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             ReduceEntriesTask<K,V> nextRight,
+             BiFunction<Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.reducer = reducer;
+        }
+        public final Map.Entry<K,V> getRawResult() { return result; }
+        public final void compute() {
+            final BiFunction<Map.Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer;
+            if ((reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new ReduceEntriesTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, reducer)).fork();
+                }
+                Map.Entry<K,V> r = null;
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = (r == null) ? p : reducer.apply(r, p);
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    ReduceEntriesTask<K,V>
+                        t = (ReduceEntriesTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        Map.Entry<K,V> tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceKeysTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final Function<? super K, ? extends U> transformer;
+        final BiFunction<? super U, ? super U, ? extends U> reducer;
+        U result;
+        MapReduceKeysTask<K,V,U> rights, nextRight;
+        MapReduceKeysTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceKeysTask<K,V,U> nextRight,
+             Function<? super K, ? extends U> transformer,
+             BiFunction<? super U, ? super U, ? extends U> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.reducer = reducer;
+        }
+        public final U getRawResult() { return result; }
+        public final void compute() {
+            final Function<? super K, ? extends U> transformer;
+            final BiFunction<? super U, ? super U, ? extends U> reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceKeysTask<K,V,U>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, reducer)).fork();
+                }
+                U r = null;
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply((K)p.key)) != null)
+                        r = (r == null) ? u : reducer.apply(r, u);
+                }
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceKeysTask<K,V,U>
+                        t = (MapReduceKeysTask<K,V,U>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        U tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceValuesTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final Function<? super V, ? extends U> transformer;
+        final BiFunction<? super U, ? super U, ? extends U> reducer;
+        U result;
+        MapReduceValuesTask<K,V,U> rights, nextRight;
+        MapReduceValuesTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceValuesTask<K,V,U> nextRight,
+             Function<? super V, ? extends U> transformer,
+             BiFunction<? super U, ? super U, ? extends U> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.reducer = reducer;
+        }
+        public final U getRawResult() { return result; }
+        public final void compute() {
+            final Function<? super V, ? extends U> transformer;
+            final BiFunction<? super U, ? super U, ? extends U> reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceValuesTask<K,V,U>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, reducer)).fork();
+                }
+                U r = null;
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply(p.val)) != null)
+                        r = (r == null) ? u : reducer.apply(r, u);
+                }
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceValuesTask<K,V,U>
+                        t = (MapReduceValuesTask<K,V,U>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        U tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceEntriesTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final Function<Map.Entry<K,V>, ? extends U> transformer;
+        final BiFunction<? super U, ? super U, ? extends U> reducer;
+        U result;
+        MapReduceEntriesTask<K,V,U> rights, nextRight;
+        MapReduceEntriesTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceEntriesTask<K,V,U> nextRight,
+             Function<Map.Entry<K,V>, ? extends U> transformer,
+             BiFunction<? super U, ? super U, ? extends U> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.reducer = reducer;
+        }
+        public final U getRawResult() { return result; }
+        public final void compute() {
+            final Function<Map.Entry<K,V>, ? extends U> transformer;
+            final BiFunction<? super U, ? super U, ? extends U> reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceEntriesTask<K,V,U>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, reducer)).fork();
+                }
+                U r = null;
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply(p)) != null)
+                        r = (r == null) ? u : reducer.apply(r, u);
+                }
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceEntriesTask<K,V,U>
+                        t = (MapReduceEntriesTask<K,V,U>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        U tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceMappingsTask<K,V,U>
+        extends BulkTask<K,V,U> {
+        final BiFunction<? super K, ? super V, ? extends U> transformer;
+        final BiFunction<? super U, ? super U, ? extends U> reducer;
+        U result;
+        MapReduceMappingsTask<K,V,U> rights, nextRight;
+        MapReduceMappingsTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceMappingsTask<K,V,U> nextRight,
+             BiFunction<? super K, ? super V, ? extends U> transformer,
+             BiFunction<? super U, ? super U, ? extends U> reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.reducer = reducer;
+        }
+        public final U getRawResult() { return result; }
+        public final void compute() {
+            final BiFunction<? super K, ? super V, ? extends U> transformer;
+            final BiFunction<? super U, ? super U, ? extends U> reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceMappingsTask<K,V,U>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, reducer)).fork();
+                }
+                U r = null;
+                for (Node<K,V> p; (p = advance()) != null; ) {
+                    U u;
+                    if ((u = transformer.apply((K)p.key, p.val)) != null)
+                        r = (r == null) ? u : reducer.apply(r, u);
+                }
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceMappingsTask<K,V,U>
+                        t = (MapReduceMappingsTask<K,V,U>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        U tr, sr;
+                        if ((sr = s.result) != null)
+                            t.result = (((tr = t.result) == null) ? sr :
+                                        reducer.apply(tr, sr));
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceKeysToDoubleTask<K,V>
+        extends BulkTask<K,V,Double> {
+        final ToDoubleFunction<? super K> transformer;
+        final DoubleBinaryOperator reducer;
+        final double basis;
+        double result;
+        MapReduceKeysToDoubleTask<K,V> rights, nextRight;
+        MapReduceKeysToDoubleTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceKeysToDoubleTask<K,V> nextRight,
+             ToDoubleFunction<? super K> transformer,
+             double basis,
+             DoubleBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Double getRawResult() { return result; }
+        public final void compute() {
+            final ToDoubleFunction<? super K> transformer;
+            final DoubleBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                double r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceKeysToDoubleTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsDouble(r, transformer.applyAsDouble((K)p.key));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceKeysToDoubleTask<K,V>
+                        t = (MapReduceKeysToDoubleTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsDouble(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceValuesToDoubleTask<K,V>
+        extends BulkTask<K,V,Double> {
+        final ToDoubleFunction<? super V> transformer;
+        final DoubleBinaryOperator reducer;
+        final double basis;
+        double result;
+        MapReduceValuesToDoubleTask<K,V> rights, nextRight;
+        MapReduceValuesToDoubleTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceValuesToDoubleTask<K,V> nextRight,
+             ToDoubleFunction<? super V> transformer,
+             double basis,
+             DoubleBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Double getRawResult() { return result; }
+        public final void compute() {
+            final ToDoubleFunction<? super V> transformer;
+            final DoubleBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                double r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceValuesToDoubleTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.val));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceValuesToDoubleTask<K,V>
+                        t = (MapReduceValuesToDoubleTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsDouble(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceEntriesToDoubleTask<K,V>
+        extends BulkTask<K,V,Double> {
+        final ToDoubleFunction<Map.Entry<K,V>> transformer;
+        final DoubleBinaryOperator reducer;
+        final double basis;
+        double result;
+        MapReduceEntriesToDoubleTask<K,V> rights, nextRight;
+        MapReduceEntriesToDoubleTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceEntriesToDoubleTask<K,V> nextRight,
+             ToDoubleFunction<Map.Entry<K,V>> transformer,
+             double basis,
+             DoubleBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Double getRawResult() { return result; }
+        public final void compute() {
+            final ToDoubleFunction<Map.Entry<K,V>> transformer;
+            final DoubleBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                double r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceEntriesToDoubleTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsDouble(r, transformer.applyAsDouble(p));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceEntriesToDoubleTask<K,V>
+                        t = (MapReduceEntriesToDoubleTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsDouble(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceMappingsToDoubleTask<K,V>
+        extends BulkTask<K,V,Double> {
+        final ToDoubleBiFunction<? super K, ? super V> transformer;
+        final DoubleBinaryOperator reducer;
+        final double basis;
+        double result;
+        MapReduceMappingsToDoubleTask<K,V> rights, nextRight;
+        MapReduceMappingsToDoubleTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceMappingsToDoubleTask<K,V> nextRight,
+             ToDoubleBiFunction<? super K, ? super V> transformer,
+             double basis,
+             DoubleBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Double getRawResult() { return result; }
+        public final void compute() {
+            final ToDoubleBiFunction<? super K, ? super V> transformer;
+            final DoubleBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                double r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceMappingsToDoubleTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsDouble(r, transformer.applyAsDouble((K)p.key, p.val));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceMappingsToDoubleTask<K,V>
+                        t = (MapReduceMappingsToDoubleTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsDouble(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceKeysToLongTask<K,V>
+        extends BulkTask<K,V,Long> {
+        final ToLongFunction<? super K> transformer;
+        final LongBinaryOperator reducer;
+        final long basis;
+        long result;
+        MapReduceKeysToLongTask<K,V> rights, nextRight;
+        MapReduceKeysToLongTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceKeysToLongTask<K,V> nextRight,
+             ToLongFunction<? super K> transformer,
+             long basis,
+             LongBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Long getRawResult() { return result; }
+        public final void compute() {
+            final ToLongFunction<? super K> transformer;
+            final LongBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                long r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceKeysToLongTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsLong(r, transformer.applyAsLong((K)p.key));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceKeysToLongTask<K,V>
+                        t = (MapReduceKeysToLongTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsLong(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceValuesToLongTask<K,V>
+        extends BulkTask<K,V,Long> {
+        final ToLongFunction<? super V> transformer;
+        final LongBinaryOperator reducer;
+        final long basis;
+        long result;
+        MapReduceValuesToLongTask<K,V> rights, nextRight;
+        MapReduceValuesToLongTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceValuesToLongTask<K,V> nextRight,
+             ToLongFunction<? super V> transformer,
+             long basis,
+             LongBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Long getRawResult() { return result; }
+        public final void compute() {
+            final ToLongFunction<? super V> transformer;
+            final LongBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                long r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceValuesToLongTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsLong(r, transformer.applyAsLong(p.val));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceValuesToLongTask<K,V>
+                        t = (MapReduceValuesToLongTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsLong(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceEntriesToLongTask<K,V>
+        extends BulkTask<K,V,Long> {
+        final ToLongFunction<Map.Entry<K,V>> transformer;
+        final LongBinaryOperator reducer;
+        final long basis;
+        long result;
+        MapReduceEntriesToLongTask<K,V> rights, nextRight;
+        MapReduceEntriesToLongTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceEntriesToLongTask<K,V> nextRight,
+             ToLongFunction<Map.Entry<K,V>> transformer,
+             long basis,
+             LongBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Long getRawResult() { return result; }
+        public final void compute() {
+            final ToLongFunction<Map.Entry<K,V>> transformer;
+            final LongBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                long r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceEntriesToLongTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsLong(r, transformer.applyAsLong(p));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceEntriesToLongTask<K,V>
+                        t = (MapReduceEntriesToLongTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsLong(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceMappingsToLongTask<K,V>
+        extends BulkTask<K,V,Long> {
+        final ToLongBiFunction<? super K, ? super V> transformer;
+        final LongBinaryOperator reducer;
+        final long basis;
+        long result;
+        MapReduceMappingsToLongTask<K,V> rights, nextRight;
+        MapReduceMappingsToLongTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceMappingsToLongTask<K,V> nextRight,
+             ToLongBiFunction<? super K, ? super V> transformer,
+             long basis,
+             LongBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Long getRawResult() { return result; }
+        public final void compute() {
+            final ToLongBiFunction<? super K, ? super V> transformer;
+            final LongBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                long r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceMappingsToLongTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsLong(r, transformer.applyAsLong((K)p.key, p.val));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceMappingsToLongTask<K,V>
+                        t = (MapReduceMappingsToLongTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsLong(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceKeysToIntTask<K,V>
+        extends BulkTask<K,V,Integer> {
+        final ToIntFunction<? super K> transformer;
+        final IntBinaryOperator reducer;
+        final int basis;
+        int result;
+        MapReduceKeysToIntTask<K,V> rights, nextRight;
+        MapReduceKeysToIntTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceKeysToIntTask<K,V> nextRight,
+             ToIntFunction<? super K> transformer,
+             int basis,
+             IntBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Integer getRawResult() { return result; }
+        public final void compute() {
+            final ToIntFunction<? super K> transformer;
+            final IntBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                int r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceKeysToIntTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsInt(r, transformer.applyAsInt((K)p.key));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceKeysToIntTask<K,V>
+                        t = (MapReduceKeysToIntTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsInt(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceValuesToIntTask<K,V>
+        extends BulkTask<K,V,Integer> {
+        final ToIntFunction<? super V> transformer;
+        final IntBinaryOperator reducer;
+        final int basis;
+        int result;
+        MapReduceValuesToIntTask<K,V> rights, nextRight;
+        MapReduceValuesToIntTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceValuesToIntTask<K,V> nextRight,
+             ToIntFunction<? super V> transformer,
+             int basis,
+             IntBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Integer getRawResult() { return result; }
+        public final void compute() {
+            final ToIntFunction<? super V> transformer;
+            final IntBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                int r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceValuesToIntTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsInt(r, transformer.applyAsInt(p.val));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceValuesToIntTask<K,V>
+                        t = (MapReduceValuesToIntTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsInt(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceEntriesToIntTask<K,V>
+        extends BulkTask<K,V,Integer> {
+        final ToIntFunction<Map.Entry<K,V>> transformer;
+        final IntBinaryOperator reducer;
+        final int basis;
+        int result;
+        MapReduceEntriesToIntTask<K,V> rights, nextRight;
+        MapReduceEntriesToIntTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceEntriesToIntTask<K,V> nextRight,
+             ToIntFunction<Map.Entry<K,V>> transformer,
+             int basis,
+             IntBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Integer getRawResult() { return result; }
+        public final void compute() {
+            final ToIntFunction<Map.Entry<K,V>> transformer;
+            final IntBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                int r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceEntriesToIntTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsInt(r, transformer.applyAsInt(p));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceEntriesToIntTask<K,V>
+                        t = (MapReduceEntriesToIntTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsInt(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
+    static final class MapReduceMappingsToIntTask<K,V>
+        extends BulkTask<K,V,Integer> {
+        final ToIntBiFunction<? super K, ? super V> transformer;
+        final IntBinaryOperator reducer;
+        final int basis;
+        int result;
+        MapReduceMappingsToIntTask<K,V> rights, nextRight;
+        MapReduceMappingsToIntTask
+            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,
+             MapReduceMappingsToIntTask<K,V> nextRight,
+             ToIntBiFunction<? super K, ? super V> transformer,
+             int basis,
+             IntBinaryOperator reducer) {
+            super(p, b, i, f, t); this.nextRight = nextRight;
+            this.transformer = transformer;
+            this.basis = basis; this.reducer = reducer;
+        }
+        public final Integer getRawResult() { return result; }
+        public final void compute() {
+            final ToIntBiFunction<? super K, ? super V> transformer;
+            final IntBinaryOperator reducer;
+            if ((transformer = this.transformer) != null &&
+                (reducer = this.reducer) != null) {
+                int r = this.basis;
+                for (int i = baseIndex, f, h; batch > 0 &&
+                         (h = ((f = baseLimit) + i) >>> 1) > i;) {
+                    addToPendingCount(1);
+                    (rights = new MapReduceMappingsToIntTask<K,V>
+                     (this, batch >>>= 1, baseLimit = h, f, tab,
+                      rights, transformer, r, reducer)).fork();
+                }
+                for (Node<K,V> p; (p = advance()) != null; )
+                    r = reducer.applyAsInt(r, transformer.applyAsInt((K)p.key, p.val));
+                result = r;
+                CountedCompleter<?> c;
+                for (c = firstComplete(); c != null; c = c.nextComplete()) {
+                    MapReduceMappingsToIntTask<K,V>
+                        t = (MapReduceMappingsToIntTask<K,V>)c,
+                        s = t.rights;
+                    while (s != null) {
+                        t.result = reducer.applyAsInt(t.result, s.result);
+                        s = t.rights = s.nextRight;
+                    }
+                }
+            }
+        }
+    }
+
     // Unsafe mechanics
-    private static final sun.misc.Unsafe UNSAFE;
-    private static final long SBASE;
-    private static final int SSHIFT;
-    private static final long TBASE;
-    private static final int TSHIFT;
-    private static final long HASHSEED_OFFSET;
-    private static final long SEGSHIFT_OFFSET;
-    private static final long SEGMASK_OFFSET;
-    private static final long SEGMENTS_OFFSET;
+    private static final sun.misc.Unsafe U;
+    private static final long SIZECTL;
+    private static final long TRANSFERINDEX;
+    private static final long TRANSFERORIGIN;
+    private static final long BASECOUNT;
+    private static final long CELLSBUSY;
+    private static final long CELLVALUE;
+    private static final long ABASE;
+    private static final int ASHIFT;
 
     static {
-        int ss, ts;
         try {
-            UNSAFE = sun.misc.Unsafe.getUnsafe();
-            Class<?> tc = HashEntry[].class;
-            Class<?> sc = Segment[].class;
-            TBASE = UNSAFE.arrayBaseOffset(tc);
-            SBASE = UNSAFE.arrayBaseOffset(sc);
-            ts = UNSAFE.arrayIndexScale(tc);
-            ss = UNSAFE.arrayIndexScale(sc);
-            HASHSEED_OFFSET = UNSAFE.objectFieldOffset(
-                ConcurrentHashMap.class.getDeclaredField("hashSeed"));
-            SEGSHIFT_OFFSET = UNSAFE.objectFieldOffset(
-                ConcurrentHashMap.class.getDeclaredField("segmentShift"));
-            SEGMASK_OFFSET = UNSAFE.objectFieldOffset(
-                ConcurrentHashMap.class.getDeclaredField("segmentMask"));
-            SEGMENTS_OFFSET = UNSAFE.objectFieldOffset(
-                ConcurrentHashMap.class.getDeclaredField("segments"));
+            U = sun.misc.Unsafe.getUnsafe();
+            Class<?> k = ConcurrentHashMap.class;
+            SIZECTL = U.objectFieldOffset
+                (k.getDeclaredField("sizeCtl"));
+            TRANSFERINDEX = U.objectFieldOffset
+                (k.getDeclaredField("transferIndex"));
+            TRANSFERORIGIN = U.objectFieldOffset
+                (k.getDeclaredField("transferOrigin"));
+            BASECOUNT = U.objectFieldOffset
+                (k.getDeclaredField("baseCount"));
+            CELLSBUSY = U.objectFieldOffset
+                (k.getDeclaredField("cellsBusy"));
+            Class<?> ck = Cell.class;
+            CELLVALUE = U.objectFieldOffset
+                (ck.getDeclaredField("value"));
+            Class<?> sc = Node[].class;
+            ABASE = U.arrayBaseOffset(sc);
+            int scale = U.arrayIndexScale(sc);
+            if ((scale & (scale - 1)) != 0)
+                throw new Error("data type scale not a power of two");
+            ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
         } catch (Exception e) {
             throw new Error(e);
         }
-        if ((ss & (ss-1)) != 0 || (ts & (ts-1)) != 0)
-            throw new Error("data type scale not a power of two");
-        SSHIFT = 31 - Integer.numberOfLeadingZeros(ss);
-        TSHIFT = 31 - Integer.numberOfLeadingZeros(ts);
     }
-
 }