changeset 29218:a2c7a365dde4

8071600: Add a flat-mapping collector Reviewed-by: smarks, chegar, briangoetz
author psandoz
date Fri, 27 Feb 2015 09:58:25 +0100
parents 874d76e4699d
children 33fb011789eb
files jdk/src/java.base/share/classes/java/util/stream/Collectors.java jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/CollectorsTest.java jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/FlatMapOpTest.java jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/TabulatorsTest.java
diffstat 4 files changed, 816 insertions(+), 624 deletions(-) [+]
line wrap: on
line diff
--- a/jdk/src/java.base/share/classes/java/util/stream/Collectors.java	Wed Jul 05 20:22:22 2017 +0200
+++ b/jdk/src/java.base/share/classes/java/util/stream/Collectors.java	Fri Feb 27 09:58:25 2015 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -404,6 +404,54 @@
     }
 
     /**
+     * Adapts a {@code Collector} accepting elements of type {@code U} to one
+     * accepting elements of type {@code T} by applying a flat mapping function
+     * to each input element before accumulation.  The flat mapping function
+     * maps an input element to a {@link Stream stream} covering zero or more
+     * output elements that are then accumulated downstream.  Each mapped stream
+     * is {@link java.util.stream.BaseStream#close() closed} after its contents
+     * have been placed downstream.  (If a mapped stream is {@code null}
+     * an empty stream is used, instead.)
+     *
+     * @apiNote
+     * The {@code flatMapping()} collectors are most useful when used in a
+     * multi-level reduction, such as downstream of a {@code groupingBy} or
+     * {@code partitioningBy}.  For example, given a stream of
+     * {@code Order}, to accumulate the set of line items for each customer:
+     * <pre>{@code
+     *     Map<String, Set<LineItem>> itemsByCustomerName
+     *         = orders.stream().collect(groupingBy(Order::getCustomerName,
+     *                                              flatMapping(order -> order.getLineItems().stream(), toSet())));
+     * }</pre>
+     *
+     * @param <T> the type of the input elements
+     * @param <U> type of elements accepted by downstream collector
+     * @param <A> intermediate accumulation type of the downstream collector
+     * @param <R> result type of collector
+     * @param mapper a function to be applied to the input elements, which
+     * returns a stream of results
+     * @param downstream a collector which will receive the elements of the
+     * stream returned by mapper
+     * @return a collector which applies the mapping function to the input
+     * elements and provides the flat mapped results to the downstream collector
+     * @since 1.9
+     */
+    public static <T, U, A, R>
+    Collector<T, ?, R> flatMapping(Function<? super T, ? extends Stream<? extends U>> mapper,
+                                   Collector<? super U, A, R> downstream) {
+        BiConsumer<A, ? super U> downstreamAccumulator = downstream.accumulator();
+        return new CollectorImpl<>(downstream.supplier(),
+                            (r, t) -> {
+                                try (Stream<? extends U> result = mapper.apply(t)) {
+                                    if (result != null)
+                                        result.sequential().forEach(u -> downstreamAccumulator.accept(r, u));
+                                }
+                            },
+                            downstream.combiner(), downstream.finisher(),
+                            downstream.characteristics());
+    }
+
+    /**
      * Adapts a {@code Collector} to perform an additional finishing
      * transformation.  For example, one could adapt the {@link #toList()}
      * collector to always produce an immutable list with:
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/CollectorsTest.java	Fri Feb 27 09:58:25 2015 +0100
@@ -0,0 +1,701 @@
+/*
+ * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package org.openjdk.tests.java.util.stream;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.StringJoiner;
+import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentSkipListMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+import java.util.stream.LambdaTestHelpers;
+import java.util.stream.OpTestCase;
+import java.util.stream.Stream;
+import java.util.stream.StreamOpFlagTestHelper;
+import java.util.stream.StreamTestDataProvider;
+import java.util.stream.TestData;
+
+import org.testng.annotations.Test;
+
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.flatMapping;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.groupingByConcurrent;
+import static java.util.stream.Collectors.mapping;
+import static java.util.stream.Collectors.partitioningBy;
+import static java.util.stream.Collectors.reducing;
+import static java.util.stream.Collectors.toCollection;
+import static java.util.stream.Collectors.toConcurrentMap;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toMap;
+import static java.util.stream.Collectors.toSet;
+import static java.util.stream.LambdaTestHelpers.assertContents;
+import static java.util.stream.LambdaTestHelpers.assertContentsUnordered;
+import static java.util.stream.LambdaTestHelpers.mDoubler;
+
+/*
+ * @test
+ * @bug 8071600
+ * @summary Test for collectors.
+ */
+public class CollectorsTest extends OpTestCase {
+
+    private static abstract class CollectorAssertion<T, U> {
+        abstract void assertValue(U value,
+                                  Supplier<Stream<T>> source,
+                                  boolean ordered) throws ReflectiveOperationException;
+    }
+
+    static class MappingAssertion<T, V, R> extends CollectorAssertion<T, R> {
+        private final Function<T, V> mapper;
+        private final CollectorAssertion<V, R> downstream;
+
+        MappingAssertion(Function<T, V> mapper, CollectorAssertion<V, R> downstream) {
+            this.mapper = mapper;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(R value, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            downstream.assertValue(value,
+                                   () -> source.get().map(mapper::apply),
+                                   ordered);
+        }
+    }
+
+    static class FlatMappingAssertion<T, V, R> extends CollectorAssertion<T, R> {
+        private final Function<T, Stream<V>> mapper;
+        private final CollectorAssertion<V, R> downstream;
+
+        FlatMappingAssertion(Function<T, Stream<V>> mapper,
+                             CollectorAssertion<V, R> downstream) {
+            this.mapper = mapper;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(R value, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            downstream.assertValue(value,
+                                   () -> source.get().flatMap(mapper::apply),
+                                   ordered);
+        }
+    }
+
+    static class GroupingByAssertion<T, K, V, M extends Map<K, ? extends V>> extends CollectorAssertion<T, M> {
+        private final Class<? extends Map> clazz;
+        private final Function<T, K> classifier;
+        private final CollectorAssertion<T,V> downstream;
+
+        GroupingByAssertion(Function<T, K> classifier, Class<? extends Map> clazz,
+                            CollectorAssertion<T, V> downstream) {
+            this.clazz = clazz;
+            this.classifier = classifier;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(M map,
+                         Supplier<Stream<T>> source,
+                         boolean ordered) throws ReflectiveOperationException {
+            if (!clazz.isAssignableFrom(map.getClass()))
+                fail(String.format("Class mismatch in GroupingByAssertion: %s, %s", clazz, map.getClass()));
+            assertContentsUnordered(map.keySet(), source.get().map(classifier).collect(toSet()));
+            for (Map.Entry<K, ? extends V> entry : map.entrySet()) {
+                K key = entry.getKey();
+                downstream.assertValue(entry.getValue(),
+                                       () -> source.get().filter(e -> classifier.apply(e).equals(key)),
+                                       ordered);
+            }
+        }
+    }
+
+    static class ToMapAssertion<T, K, V, M extends Map<K,V>> extends CollectorAssertion<T, M> {
+        private final Class<? extends Map> clazz;
+        private final Function<T, K> keyFn;
+        private final Function<T, V> valueFn;
+        private final BinaryOperator<V> mergeFn;
+
+        ToMapAssertion(Function<T, K> keyFn,
+                       Function<T, V> valueFn,
+                       BinaryOperator<V> mergeFn,
+                       Class<? extends Map> clazz) {
+            this.clazz = clazz;
+            this.keyFn = keyFn;
+            this.valueFn = valueFn;
+            this.mergeFn = mergeFn;
+        }
+
+        @Override
+        void assertValue(M map, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            if (!clazz.isAssignableFrom(map.getClass()))
+                fail(String.format("Class mismatch in ToMapAssertion: %s, %s", clazz, map.getClass()));
+            Set<K> uniqueKeys = source.get().map(keyFn).collect(toSet());
+            assertEquals(uniqueKeys, map.keySet());
+            source.get().forEach(t -> {
+                K key = keyFn.apply(t);
+                V v = source.get()
+                            .filter(e -> key.equals(keyFn.apply(e)))
+                            .map(valueFn)
+                            .reduce(mergeFn)
+                            .get();
+                assertEquals(map.get(key), v);
+            });
+        }
+    }
+
+    static class PartitioningByAssertion<T, D> extends CollectorAssertion<T, Map<Boolean,D>> {
+        private final Predicate<T> predicate;
+        private final CollectorAssertion<T,D> downstream;
+
+        PartitioningByAssertion(Predicate<T> predicate, CollectorAssertion<T, D> downstream) {
+            this.predicate = predicate;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(Map<Boolean, D> map,
+                         Supplier<Stream<T>> source,
+                         boolean ordered) throws ReflectiveOperationException {
+            if (!Map.class.isAssignableFrom(map.getClass()))
+                fail(String.format("Class mismatch in PartitioningByAssertion: %s", map.getClass()));
+            assertEquals(2, map.size());
+            downstream.assertValue(map.get(true), () -> source.get().filter(predicate), ordered);
+            downstream.assertValue(map.get(false), () -> source.get().filter(predicate.negate()), ordered);
+        }
+    }
+
+    static class ToListAssertion<T> extends CollectorAssertion<T, List<T>> {
+        @Override
+        void assertValue(List<T> value, Supplier<Stream<T>> source, boolean ordered)
+                throws ReflectiveOperationException {
+            if (!List.class.isAssignableFrom(value.getClass()))
+                fail(String.format("Class mismatch in ToListAssertion: %s", value.getClass()));
+            Stream<T> stream = source.get();
+            List<T> result = new ArrayList<>();
+            for (Iterator<T> it = stream.iterator(); it.hasNext(); ) // avoid capturing result::add
+                result.add(it.next());
+            if (StreamOpFlagTestHelper.isStreamOrdered(stream) && ordered)
+                assertContents(value, result);
+            else
+                assertContentsUnordered(value, result);
+        }
+    }
+
+    static class ToCollectionAssertion<T> extends CollectorAssertion<T, Collection<T>> {
+        private final Class<? extends Collection> clazz;
+        private final boolean targetOrdered;
+
+        ToCollectionAssertion(Class<? extends Collection> clazz, boolean targetOrdered) {
+            this.clazz = clazz;
+            this.targetOrdered = targetOrdered;
+        }
+
+        @Override
+        void assertValue(Collection<T> value, Supplier<Stream<T>> source, boolean ordered)
+                throws ReflectiveOperationException {
+            if (!clazz.isAssignableFrom(value.getClass()))
+                fail(String.format("Class mismatch in ToCollectionAssertion: %s, %s", clazz, value.getClass()));
+            Stream<T> stream = source.get();
+            Collection<T> result = clazz.newInstance();
+            for (Iterator<T> it = stream.iterator(); it.hasNext(); ) // avoid capturing result::add
+                result.add(it.next());
+            if (StreamOpFlagTestHelper.isStreamOrdered(stream) && targetOrdered && ordered)
+                assertContents(value, result);
+            else
+                assertContentsUnordered(value, result);
+        }
+    }
+
+    static class ReducingAssertion<T, U> extends CollectorAssertion<T, U> {
+        private final U identity;
+        private final Function<T, U> mapper;
+        private final BinaryOperator<U> reducer;
+
+        ReducingAssertion(U identity, Function<T, U> mapper, BinaryOperator<U> reducer) {
+            this.identity = identity;
+            this.mapper = mapper;
+            this.reducer = reducer;
+        }
+
+        @Override
+        void assertValue(U value, Supplier<Stream<T>> source, boolean ordered)
+                throws ReflectiveOperationException {
+            Optional<U> reduced = source.get().map(mapper).reduce(reducer);
+            if (value == null)
+                assertTrue(!reduced.isPresent());
+            else if (!reduced.isPresent()) {
+                assertEquals(value, identity);
+            }
+            else {
+                assertEquals(value, reduced.get());
+            }
+        }
+    }
+
+    private <T> ResultAsserter<T> mapTabulationAsserter(boolean ordered) {
+        return (act, exp, ord, par) -> {
+            if (par && (!ordered || !ord)) {
+                CollectorsTest.nestedMapEqualityAssertion(act, exp);
+            }
+            else {
+                LambdaTestHelpers.assertContentsEqual(act, exp);
+            }
+        };
+    }
+
+    private<T, M extends Map>
+    void exerciseMapCollection(TestData<T, Stream<T>> data,
+                               Collector<T, ?, ? extends M> collector,
+                               CollectorAssertion<T, M> assertion)
+            throws ReflectiveOperationException {
+        boolean ordered = !collector.characteristics().contains(Collector.Characteristics.UNORDERED);
+
+        M m = withData(data)
+                .terminal(s -> s.collect(collector))
+                .resultAsserter(mapTabulationAsserter(ordered))
+                .exercise();
+        assertion.assertValue(m, () -> data.stream(), ordered);
+
+        m = withData(data)
+                .terminal(s -> s.unordered().collect(collector))
+                .resultAsserter(mapTabulationAsserter(ordered))
+                .exercise();
+        assertion.assertValue(m, () -> data.stream(), false);
+    }
+
+    private static void nestedMapEqualityAssertion(Object o1, Object o2) {
+        if (o1 instanceof Map) {
+            Map m1 = (Map) o1;
+            Map m2 = (Map) o2;
+            assertContentsUnordered(m1.keySet(), m2.keySet());
+            for (Object k : m1.keySet())
+                nestedMapEqualityAssertion(m1.get(k), m2.get(k));
+        }
+        else if (o1 instanceof Collection) {
+            assertContentsUnordered(((Collection) o1), ((Collection) o2));
+        }
+        else
+            assertEquals(o1, o2);
+    }
+
+    private<T, R> void assertCollect(TestData.OfRef<T> data,
+                                     Collector<T, ?, R> collector,
+                                     Function<Stream<T>, R> streamReduction) {
+        R check = streamReduction.apply(data.stream());
+        withData(data).terminal(s -> s.collect(collector)).expectedResult(check).exercise();
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testReducing(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        assertCollect(data, Collectors.reducing(0, Integer::sum),
+                      s -> s.reduce(0, Integer::sum));
+        assertCollect(data, Collectors.reducing(Integer.MAX_VALUE, Integer::min),
+                      s -> s.min(Integer::compare).orElse(Integer.MAX_VALUE));
+        assertCollect(data, Collectors.reducing(Integer.MIN_VALUE, Integer::max),
+                      s -> s.max(Integer::compare).orElse(Integer.MIN_VALUE));
+
+        assertCollect(data, Collectors.reducing(Integer::sum),
+                      s -> s.reduce(Integer::sum));
+        assertCollect(data, Collectors.minBy(Comparator.naturalOrder()),
+                      s -> s.min(Integer::compare));
+        assertCollect(data, Collectors.maxBy(Comparator.naturalOrder()),
+                      s -> s.max(Integer::compare));
+
+        assertCollect(data, Collectors.reducing(0, x -> x*2, Integer::sum),
+                      s -> s.map(x -> x*2).reduce(0, Integer::sum));
+
+        assertCollect(data, Collectors.summingLong(x -> x * 2L),
+                      s -> s.map(x -> x*2L).reduce(0L, Long::sum));
+        assertCollect(data, Collectors.summingInt(x -> x * 2),
+                      s -> s.map(x -> x*2).reduce(0, Integer::sum));
+        assertCollect(data, Collectors.summingDouble(x -> x * 2.0d),
+                      s -> s.map(x -> x * 2.0d).reduce(0.0d, Double::sum));
+
+        assertCollect(data, Collectors.averagingInt(x -> x * 2),
+                      s -> s.mapToInt(x -> x * 2).average().orElse(0));
+        assertCollect(data, Collectors.averagingLong(x -> x * 2),
+                      s -> s.mapToLong(x -> x * 2).average().orElse(0));
+        assertCollect(data, Collectors.averagingDouble(x -> x * 2),
+                      s -> s.mapToDouble(x -> x * 2).average().orElse(0));
+
+        // Test explicit Collector.of
+        Collector<Integer, long[], Double> avg2xint = Collector.of(() -> new long[2],
+                                                                   (a, b) -> {
+                                                                       a[0] += b * 2;
+                                                                       a[1]++;
+                                                                   },
+                                                                   (a, b) -> {
+                                                                       a[0] += b[0];
+                                                                       a[1] += b[1];
+                                                                       return a;
+                                                                   },
+                                                                   a -> a[1] == 0 ? 0.0d : (double) a[0] / a[1]);
+        assertCollect(data, avg2xint,
+                      s -> s.mapToInt(x -> x * 2).average().orElse(0));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testJoining(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(Collectors.joining()))
+                .expectedResult(join(data, ""))
+                .exercise();
+
+        Collector<String, StringBuilder, String> likeJoining = Collector.of(StringBuilder::new, StringBuilder::append, (sb1, sb2) -> sb1.append(sb2.toString()), StringBuilder::toString);
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(likeJoining))
+                .expectedResult(join(data, ""))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(Collectors.joining(",")))
+                .expectedResult(join(data, ","))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(Collectors.joining(",", "[", "]")))
+                .expectedResult("[" + join(data, ",") + "]")
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString)
+                                .collect(StringBuilder::new, StringBuilder::append, StringBuilder::append)
+                                .toString())
+                .expectedResult(join(data, ""))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString)
+                                .collect(() -> new StringJoiner(","),
+                                         (sj, cs) -> sj.add(cs),
+                                         (j1, j2) -> j1.merge(j2))
+                                .toString())
+                .expectedResult(join(data, ","))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString)
+                                .collect(() -> new StringJoiner(",", "[", "]"),
+                                         (sj, cs) -> sj.add(cs),
+                                         (j1, j2) -> j1.merge(j2))
+                                .toString())
+                .expectedResult("[" + join(data, ",") + "]")
+                .exercise();
+    }
+
+    private<T> String join(TestData.OfRef<T> data, String delim) {
+        StringBuilder sb = new StringBuilder();
+        boolean first = true;
+        for (T i : data) {
+            if (!first)
+                sb.append(delim);
+            sb.append(i.toString());
+            first = false;
+        }
+        return sb.toString();
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testSimpleToMap(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> keyFn = i -> i * 2;
+        Function<Integer, Integer> valueFn = i -> i * 4;
+
+        List<Integer> dataAsList = Arrays.asList(data.stream().toArray(Integer[]::new));
+        Set<Integer> dataAsSet = new HashSet<>(dataAsList);
+
+        BinaryOperator<Integer> sum = Integer::sum;
+        for (BinaryOperator<Integer> op : Arrays.asList((u, v) -> u,
+                                                        (u, v) -> v,
+                                                        sum)) {
+            try {
+                exerciseMapCollection(data, toMap(keyFn, valueFn),
+                                      new ToMapAssertion<>(keyFn, valueFn, op, HashMap.class));
+                if (dataAsList.size() != dataAsSet.size())
+                    fail("Expected ISE on input with duplicates");
+            }
+            catch (IllegalStateException e) {
+                if (dataAsList.size() == dataAsSet.size())
+                    fail("Expected no ISE on input without duplicates");
+            }
+
+            exerciseMapCollection(data, toMap(keyFn, valueFn, op),
+                                  new ToMapAssertion<>(keyFn, valueFn, op, HashMap.class));
+
+            exerciseMapCollection(data, toMap(keyFn, valueFn, op, TreeMap::new),
+                                  new ToMapAssertion<>(keyFn, valueFn, op, TreeMap.class));
+        }
+
+        // For concurrent maps, only use commutative merge functions
+        try {
+            exerciseMapCollection(data, toConcurrentMap(keyFn, valueFn),
+                                  new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentHashMap.class));
+            if (dataAsList.size() != dataAsSet.size())
+                fail("Expected ISE on input with duplicates");
+        }
+        catch (IllegalStateException e) {
+            if (dataAsList.size() == dataAsSet.size())
+                fail("Expected no ISE on input without duplicates");
+        }
+
+        exerciseMapCollection(data, toConcurrentMap(keyFn, valueFn, sum),
+                              new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentHashMap.class));
+
+        exerciseMapCollection(data, toConcurrentMap(keyFn, valueFn, sum, ConcurrentSkipListMap::new),
+                              new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentSkipListMap.class));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testSimpleGroupingBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+
+        // Single-level groupBy
+        exerciseMapCollection(data, groupingBy(classifier),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new ToListAssertion<>()));
+        exerciseMapCollection(data, groupingByConcurrent(classifier),
+                              new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                                                        new ToListAssertion<>()));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                              groupingBy(classifier, TreeMap::new, toCollection(HashSet::new)),
+                              new GroupingByAssertion<>(classifier, TreeMap.class,
+                                                        new ToCollectionAssertion<Integer>(HashSet.class, false)));
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new,
+                                                   toCollection(HashSet::new)),
+                              new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                                                        new ToCollectionAssertion<Integer>(HashSet.class, false)));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupingByWithMapping(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+        Function<Integer, Integer> mapper = i -> i * 2;
+
+        exerciseMapCollection(data,
+                              groupingBy(classifier, mapping(mapper, toList())),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new MappingAssertion<>(mapper,
+                                                                               new ToListAssertion<>())));
+    }
+
+    @Test
+    public void testFlatMappingClose() {
+        Function<Integer, Integer> classifier = i -> i;
+        AtomicInteger ai = new AtomicInteger();
+        Function<Integer, Stream<Integer>> flatMapper = i -> Stream.of(i, i).onClose(ai::getAndIncrement);
+        Map<Integer, List<Integer>> m = Stream.of(1, 2).collect(groupingBy(classifier, flatMapping(flatMapper, toList())));
+        assertEquals(m.size(), ai.get());
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupingByWithFlatMapping(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+        Function<Integer, Stream<Integer>> flatMapperByNull = i -> null;
+        Function<Integer, Stream<Integer>> flatMapperBy0 = i -> Stream.empty();
+        Function<Integer, Stream<Integer>> flatMapperBy2 = i -> Stream.of(i, i);
+
+        exerciseMapCollection(data,
+                              groupingBy(classifier, flatMapping(flatMapperByNull, toList())),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new FlatMappingAssertion<>(flatMapperBy0,
+                                                                                   new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                              groupingBy(classifier, flatMapping(flatMapperBy0, toList())),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new FlatMappingAssertion<>(flatMapperBy0,
+                                                                                   new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                              groupingBy(classifier, flatMapping(flatMapperBy2, toList())),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new FlatMappingAssertion<>(flatMapperBy2,
+                                                                                   new ToListAssertion<>())));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testTwoLevelGroupingBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 6;
+        Function<Integer, Integer> classifier2 = i -> i % 23;
+
+        // Two-level groupBy
+        exerciseMapCollection(data,
+                              groupingBy(classifier, groupingBy(classifier2)),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new GroupingByAssertion<>(classifier2, HashMap.class,
+                                                                                  new ToListAssertion<>())));
+        // with concurrent as upstream
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, groupingBy(classifier2)),
+                              new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                                                        new GroupingByAssertion<>(classifier2, HashMap.class,
+                                                                                  new ToListAssertion<>())));
+        // with concurrent as downstream
+        exerciseMapCollection(data,
+                              groupingBy(classifier, groupingByConcurrent(classifier2)),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new GroupingByAssertion<>(classifier2, ConcurrentHashMap.class,
+                                                                                  new ToListAssertion<>())));
+        // with concurrent as upstream and downstream
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, groupingByConcurrent(classifier2)),
+                              new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                                                        new GroupingByAssertion<>(classifier2, ConcurrentHashMap.class,
+                                                                                  new ToListAssertion<>())));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                              groupingBy(classifier, TreeMap::new, groupingBy(classifier2, TreeMap::new, toCollection(HashSet::new))),
+                              new GroupingByAssertion<>(classifier, TreeMap.class,
+                                                        new GroupingByAssertion<>(classifier2, TreeMap.class,
+                                                                                  new ToCollectionAssertion<Integer>(HashSet.class, false))));
+        // with concurrent as upstream
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, groupingBy(classifier2, TreeMap::new, toList())),
+                              new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                                                        new GroupingByAssertion<>(classifier2, TreeMap.class,
+                                                                                  new ToListAssertion<>())));
+        // with concurrent as downstream
+        exerciseMapCollection(data,
+                              groupingBy(classifier, TreeMap::new, groupingByConcurrent(classifier2, ConcurrentSkipListMap::new, toList())),
+                              new GroupingByAssertion<>(classifier, TreeMap.class,
+                                                        new GroupingByAssertion<>(classifier2, ConcurrentSkipListMap.class,
+                                                                                  new ToListAssertion<>())));
+        // with concurrent as upstream and downstream
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, groupingByConcurrent(classifier2, ConcurrentSkipListMap::new, toList())),
+                              new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                                                        new GroupingByAssertion<>(classifier2, ConcurrentSkipListMap.class,
+                                                                                  new ToListAssertion<>())));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupubgByWithReducing(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+
+        // Single-level simple reduce
+        exerciseMapCollection(data,
+                              groupingBy(classifier, reducing(0, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, reducing(0, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                                                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                              groupingBy(classifier, TreeMap::new, reducing(0, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, TreeMap.class,
+                                                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, reducing(0, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                                                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+
+        // Single-level map-reduce
+        exerciseMapCollection(data,
+                              groupingBy(classifier, reducing(0, mDoubler, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, HashMap.class,
+                                                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, reducing(0, mDoubler, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                                                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                              groupingBy(classifier, TreeMap::new, reducing(0, mDoubler, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, TreeMap.class,
+                                                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, reducing(0, mDoubler, Integer::sum)),
+                              new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                                                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testSimplePartitioningBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Predicate<Integer> classifier = i -> i % 3 == 0;
+
+        // Single-level partition to downstream List
+        exerciseMapCollection(data,
+                              partitioningBy(classifier),
+                              new PartitioningByAssertion<>(classifier, new ToListAssertion<>()));
+        exerciseMapCollection(data,
+                              partitioningBy(classifier, toList()),
+                              new PartitioningByAssertion<>(classifier, new ToListAssertion<>()));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testTwoLevelPartitioningBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Predicate<Integer> classifier = i -> i % 3 == 0;
+        Predicate<Integer> classifier2 = i -> i % 7 == 0;
+
+        // Two level partition
+        exerciseMapCollection(data,
+                              partitioningBy(classifier, partitioningBy(classifier2)),
+                              new PartitioningByAssertion<>(classifier,
+                                                            new PartitioningByAssertion(classifier2, new ToListAssertion<>())));
+
+        // Two level partition with reduce
+        exerciseMapCollection(data,
+                              partitioningBy(classifier, reducing(0, Integer::sum)),
+                              new PartitioningByAssertion<>(classifier,
+                                                            new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testComposeFinisher(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        List<Integer> asList = exerciseTerminalOps(data, s -> s.collect(toList()));
+        List<Integer> asImmutableList = exerciseTerminalOps(data, s -> s.collect(collectingAndThen(toList(), Collections::unmodifiableList)));
+        assertEquals(asList, asImmutableList);
+        try {
+            asImmutableList.add(0);
+            fail("Expecting immutable result");
+        }
+        catch (UnsupportedOperationException ignored) { }
+    }
+
+}
--- a/jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/FlatMapOpTest.java	Wed Jul 05 20:22:22 2017 +0200
+++ b/jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/FlatMapOpTest.java	Fri Feb 27 09:58:25 2015 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -34,8 +34,19 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Function;
-import java.util.stream.*;
+import java.util.function.Supplier;
+import java.util.stream.DoubleStream;
+import java.util.stream.DoubleStreamTestDataProvider;
+import java.util.stream.IntStream;
+import java.util.stream.IntStreamTestDataProvider;
+import java.util.stream.LongStream;
+import java.util.stream.LongStreamTestDataProvider;
+import java.util.stream.OpTestCase;
+import java.util.stream.Stream;
+import java.util.stream.StreamTestDataProvider;
+import java.util.stream.TestData;
 
 import static java.util.stream.LambdaTestHelpers.*;
 import static java.util.stream.ThowableHelper.checkNPE;
@@ -66,6 +77,59 @@
         exerciseOps(TestData.Factory.ofArray("LONG_STRING", new String[] {LONG_STRING}), s -> s.flatMap(flattenChars));
     }
 
+    @Test
+    public void testClose() {
+        AtomicInteger before = new AtomicInteger();
+        AtomicInteger onClose = new AtomicInteger();
+
+        Supplier<Stream<Integer>> s = () -> {
+            before.set(0); onClose.set(0);
+            return Stream.of(1, 2).peek(e -> before.getAndIncrement());
+        };
+
+        s.get().flatMap(i -> Stream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+
+        s.get().flatMapToInt(i -> IntStream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+
+        s.get().flatMapToLong(i -> LongStream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+
+        s.get().flatMapToDouble(i -> DoubleStream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+    }
+
+    @Test
+    public void testIntClose() {
+        AtomicInteger before = new AtomicInteger();
+        AtomicInteger onClose = new AtomicInteger();
+
+        IntStream.of(1, 2).peek(e -> before.getAndIncrement()).
+                flatMap(i -> IntStream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+    }
+
+    @Test
+    public void testLongClose() {
+        AtomicInteger before = new AtomicInteger();
+        AtomicInteger onClose = new AtomicInteger();
+
+        LongStream.of(1, 2).peek(e -> before.getAndIncrement()).
+                flatMap(i -> LongStream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+    }
+
+    @Test
+    public void testDoubleClose() {
+        AtomicInteger before = new AtomicInteger();
+        AtomicInteger onClose = new AtomicInteger();
+
+        DoubleStream.of(1, 2).peek(e -> before.getAndIncrement()).
+                flatMap(i -> DoubleStream.of(i, i).onClose(onClose::getAndIncrement)).count();
+        assertEquals(before.get(), onClose.get());
+    }
+
     @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
     public void testOps(String name, TestData.OfRef<Integer> data) {
         Collection<Integer> result = exerciseOps(data, s -> s.flatMap(mfId));
--- a/jdk/test/java/util/stream/test/org/openjdk/tests/java/util/stream/TabulatorsTest.java	Wed Jul 05 20:22:22 2017 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,621 +0,0 @@
-/*
- * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-package org.openjdk.tests.java.util.stream;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Comparator;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.Optional;
-import java.util.Set;
-import java.util.StringJoiner;
-import java.util.TreeMap;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentSkipListMap;
-import java.util.function.BinaryOperator;
-import java.util.function.Function;
-import java.util.function.Predicate;
-import java.util.function.Supplier;
-import java.util.stream.Collector;
-import java.util.stream.Collectors;
-import java.util.stream.LambdaTestHelpers;
-import java.util.stream.OpTestCase;
-import java.util.stream.Stream;
-import java.util.stream.StreamOpFlagTestHelper;
-import java.util.stream.StreamTestDataProvider;
-import java.util.stream.TestData;
-
-import org.testng.annotations.Test;
-
-import static java.util.stream.Collectors.collectingAndThen;
-import static java.util.stream.Collectors.groupingBy;
-import static java.util.stream.Collectors.groupingByConcurrent;
-import static java.util.stream.Collectors.partitioningBy;
-import static java.util.stream.Collectors.reducing;
-import static java.util.stream.Collectors.toCollection;
-import static java.util.stream.Collectors.toConcurrentMap;
-import static java.util.stream.Collectors.toList;
-import static java.util.stream.Collectors.toMap;
-import static java.util.stream.Collectors.toSet;
-import static java.util.stream.LambdaTestHelpers.assertContents;
-import static java.util.stream.LambdaTestHelpers.assertContentsUnordered;
-import static java.util.stream.LambdaTestHelpers.mDoubler;
-
-/**
- * TabulatorsTest
- *
- * @author Brian Goetz
- */
-@SuppressWarnings({"rawtypes", "unchecked"})
-public class TabulatorsTest extends OpTestCase {
-
-    private static abstract class TabulationAssertion<T, U> {
-        abstract void assertValue(U value,
-                                  Supplier<Stream<T>> source,
-                                  boolean ordered) throws ReflectiveOperationException;
-    }
-
-    @SuppressWarnings({"rawtypes", "unchecked"})
-    static class GroupedMapAssertion<T, K, V, M extends Map<K, ? extends V>> extends TabulationAssertion<T, M> {
-        private final Class<? extends Map> clazz;
-        private final Function<T, K> classifier;
-        private final TabulationAssertion<T,V> downstream;
-
-        protected GroupedMapAssertion(Function<T, K> classifier,
-                                      Class<? extends Map> clazz,
-                                      TabulationAssertion<T, V> downstream) {
-            this.clazz = clazz;
-            this.classifier = classifier;
-            this.downstream = downstream;
-        }
-
-        void assertValue(M map,
-                         Supplier<Stream<T>> source,
-                         boolean ordered) throws ReflectiveOperationException {
-            if (!clazz.isAssignableFrom(map.getClass()))
-                fail(String.format("Class mismatch in GroupedMapAssertion: %s, %s", clazz, map.getClass()));
-            assertContentsUnordered(map.keySet(), source.get().map(classifier).collect(toSet()));
-            for (Map.Entry<K, ? extends V> entry : map.entrySet()) {
-                K key = entry.getKey();
-                downstream.assertValue(entry.getValue(),
-                                       () -> source.get().filter(e -> classifier.apply(e).equals(key)),
-                                       ordered);
-            }
-        }
-    }
-
-    static class ToMapAssertion<T, K, V, M extends Map<K,V>> extends TabulationAssertion<T, M> {
-        private final Class<? extends Map> clazz;
-        private final Function<T, K> keyFn;
-        private final Function<T, V> valueFn;
-        private final BinaryOperator<V> mergeFn;
-
-        ToMapAssertion(Function<T, K> keyFn,
-                       Function<T, V> valueFn,
-                       BinaryOperator<V> mergeFn,
-                       Class<? extends Map> clazz) {
-            this.clazz = clazz;
-            this.keyFn = keyFn;
-            this.valueFn = valueFn;
-            this.mergeFn = mergeFn;
-        }
-
-        @Override
-        void assertValue(M map, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
-            Set<K> uniqueKeys = source.get().map(keyFn).collect(toSet());
-            assertTrue(clazz.isAssignableFrom(map.getClass()));
-            assertEquals(uniqueKeys, map.keySet());
-            source.get().forEach(t -> {
-                K key = keyFn.apply(t);
-                V v = source.get()
-                            .filter(e -> key.equals(keyFn.apply(e)))
-                            .map(valueFn)
-                            .reduce(mergeFn)
-                            .get();
-                assertEquals(map.get(key), v);
-            });
-        }
-    }
-
-    static class PartitionAssertion<T, D> extends TabulationAssertion<T, Map<Boolean,D>> {
-        private final Predicate<T> predicate;
-        private final TabulationAssertion<T,D> downstream;
-
-        protected PartitionAssertion(Predicate<T> predicate,
-                                     TabulationAssertion<T, D> downstream) {
-            this.predicate = predicate;
-            this.downstream = downstream;
-        }
-
-        void assertValue(Map<Boolean, D> map,
-                         Supplier<Stream<T>> source,
-                         boolean ordered) throws ReflectiveOperationException {
-            if (!Map.class.isAssignableFrom(map.getClass()))
-                fail(String.format("Class mismatch in PartitionAssertion: %s", map.getClass()));
-            assertEquals(2, map.size());
-            downstream.assertValue(map.get(true), () -> source.get().filter(predicate), ordered);
-            downstream.assertValue(map.get(false), () -> source.get().filter(predicate.negate()), ordered);
-        }
-    }
-
-    @SuppressWarnings({"rawtypes", "unchecked"})
-    static class ListAssertion<T> extends TabulationAssertion<T, List<T>> {
-        @Override
-        void assertValue(List<T> value, Supplier<Stream<T>> source, boolean ordered)
-                throws ReflectiveOperationException {
-            if (!List.class.isAssignableFrom(value.getClass()))
-                fail(String.format("Class mismatch in ListAssertion: %s", value.getClass()));
-            Stream<T> stream = source.get();
-            List<T> result = new ArrayList<>();
-            for (Iterator<T> it = stream.iterator(); it.hasNext(); ) // avoid capturing result::add
-                result.add(it.next());
-            if (StreamOpFlagTestHelper.isStreamOrdered(stream) && ordered)
-                assertContents(value, result);
-            else
-                assertContentsUnordered(value, result);
-        }
-    }
-
-    @SuppressWarnings({"rawtypes", "unchecked"})
-    static class CollectionAssertion<T> extends TabulationAssertion<T, Collection<T>> {
-        private final Class<? extends Collection> clazz;
-        private final boolean targetOrdered;
-
-        protected CollectionAssertion(Class<? extends Collection> clazz, boolean targetOrdered) {
-            this.clazz = clazz;
-            this.targetOrdered = targetOrdered;
-        }
-
-        @Override
-        void assertValue(Collection<T> value, Supplier<Stream<T>> source, boolean ordered)
-                throws ReflectiveOperationException {
-            if (!clazz.isAssignableFrom(value.getClass()))
-                fail(String.format("Class mismatch in CollectionAssertion: %s, %s", clazz, value.getClass()));
-            Stream<T> stream = source.get();
-            Collection<T> result = clazz.newInstance();
-            for (Iterator<T> it = stream.iterator(); it.hasNext(); ) // avoid capturing result::add
-                result.add(it.next());
-            if (StreamOpFlagTestHelper.isStreamOrdered(stream) && targetOrdered && ordered)
-                assertContents(value, result);
-            else
-                assertContentsUnordered(value, result);
-        }
-    }
-
-    static class ReduceAssertion<T, U> extends TabulationAssertion<T, U> {
-        private final U identity;
-        private final Function<T, U> mapper;
-        private final BinaryOperator<U> reducer;
-
-        ReduceAssertion(U identity, Function<T, U> mapper, BinaryOperator<U> reducer) {
-            this.identity = identity;
-            this.mapper = mapper;
-            this.reducer = reducer;
-        }
-
-        @Override
-        void assertValue(U value, Supplier<Stream<T>> source, boolean ordered)
-                throws ReflectiveOperationException {
-            Optional<U> reduced = source.get().map(mapper).reduce(reducer);
-            if (value == null)
-                assertTrue(!reduced.isPresent());
-            else if (!reduced.isPresent()) {
-                assertEquals(value, identity);
-            }
-            else {
-                assertEquals(value, reduced.get());
-            }
-        }
-    }
-
-    private <T> ResultAsserter<T> mapTabulationAsserter(boolean ordered) {
-        return (act, exp, ord, par) -> {
-            if (par && (!ordered || !ord)) {
-                TabulatorsTest.nestedMapEqualityAssertion(act, exp);
-            }
-            else {
-                LambdaTestHelpers.assertContentsEqual(act, exp);
-            }
-        };
-    }
-
-    private<T, M extends Map>
-    void exerciseMapTabulation(TestData<T, Stream<T>> data,
-                               Collector<T, ?, ? extends M> collector,
-                               TabulationAssertion<T, M> assertion)
-            throws ReflectiveOperationException {
-        boolean ordered = !collector.characteristics().contains(Collector.Characteristics.UNORDERED);
-
-        M m = withData(data)
-                .terminal(s -> s.collect(collector))
-                .resultAsserter(mapTabulationAsserter(ordered))
-                .exercise();
-        assertion.assertValue(m, () -> data.stream(), ordered);
-
-        m = withData(data)
-                .terminal(s -> s.unordered().collect(collector))
-                .resultAsserter(mapTabulationAsserter(ordered))
-                .exercise();
-        assertion.assertValue(m, () -> data.stream(), false);
-    }
-
-    private static void nestedMapEqualityAssertion(Object o1, Object o2) {
-        if (o1 instanceof Map) {
-            Map m1 = (Map) o1;
-            Map m2 = (Map) o2;
-            assertContentsUnordered(m1.keySet(), m2.keySet());
-            for (Object k : m1.keySet())
-                nestedMapEqualityAssertion(m1.get(k), m2.get(k));
-        }
-        else if (o1 instanceof Collection) {
-            assertContentsUnordered(((Collection) o1), ((Collection) o2));
-        }
-        else
-            assertEquals(o1, o2);
-    }
-
-    private<T, R> void assertCollect(TestData.OfRef<T> data,
-                                     Collector<T, ?, R> collector,
-                                     Function<Stream<T>, R> streamReduction) {
-        R check = streamReduction.apply(data.stream());
-        withData(data).terminal(s -> s.collect(collector)).expectedResult(check).exercise();
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testReduce(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        assertCollect(data, Collectors.reducing(0, Integer::sum),
-                      s -> s.reduce(0, Integer::sum));
-        assertCollect(data, Collectors.reducing(Integer.MAX_VALUE, Integer::min),
-                      s -> s.min(Integer::compare).orElse(Integer.MAX_VALUE));
-        assertCollect(data, Collectors.reducing(Integer.MIN_VALUE, Integer::max),
-                      s -> s.max(Integer::compare).orElse(Integer.MIN_VALUE));
-
-        assertCollect(data, Collectors.reducing(Integer::sum),
-                      s -> s.reduce(Integer::sum));
-        assertCollect(data, Collectors.minBy(Comparator.naturalOrder()),
-                      s -> s.min(Integer::compare));
-        assertCollect(data, Collectors.maxBy(Comparator.naturalOrder()),
-                      s -> s.max(Integer::compare));
-
-        assertCollect(data, Collectors.reducing(0, x -> x*2, Integer::sum),
-                      s -> s.map(x -> x*2).reduce(0, Integer::sum));
-
-        assertCollect(data, Collectors.summingLong(x -> x * 2L),
-                      s -> s.map(x -> x*2L).reduce(0L, Long::sum));
-        assertCollect(data, Collectors.summingInt(x -> x * 2),
-                      s -> s.map(x -> x*2).reduce(0, Integer::sum));
-        assertCollect(data, Collectors.summingDouble(x -> x * 2.0d),
-                      s -> s.map(x -> x * 2.0d).reduce(0.0d, Double::sum));
-
-        assertCollect(data, Collectors.averagingInt(x -> x * 2),
-                      s -> s.mapToInt(x -> x * 2).average().orElse(0));
-        assertCollect(data, Collectors.averagingLong(x -> x * 2),
-                      s -> s.mapToLong(x -> x * 2).average().orElse(0));
-        assertCollect(data, Collectors.averagingDouble(x -> x * 2),
-                      s -> s.mapToDouble(x -> x * 2).average().orElse(0));
-
-        // Test explicit Collector.of
-        Collector<Integer, long[], Double> avg2xint = Collector.of(() -> new long[2],
-                                                                   (a, b) -> {
-                                                                       a[0] += b * 2;
-                                                                       a[1]++;
-                                                                   },
-                                                                   (a, b) -> {
-                                                                       a[0] += b[0];
-                                                                       a[1] += b[1];
-                                                                       return a;
-                                                                   },
-                                                                   a -> a[1] == 0 ? 0.0d : (double) a[0] / a[1]);
-        assertCollect(data, avg2xint,
-                      s -> s.mapToInt(x -> x * 2).average().orElse(0));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testJoin(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        withData(data)
-                .terminal(s -> s.map(Object::toString).collect(Collectors.joining()))
-                .expectedResult(join(data, ""))
-                .exercise();
-
-        Collector<String, StringBuilder, String> likeJoining = Collector.of(StringBuilder::new, StringBuilder::append, (sb1, sb2) -> sb1.append(sb2.toString()), StringBuilder::toString);
-        withData(data)
-                .terminal(s -> s.map(Object::toString).collect(likeJoining))
-                .expectedResult(join(data, ""))
-                .exercise();
-
-        withData(data)
-                .terminal(s -> s.map(Object::toString).collect(Collectors.joining(",")))
-                .expectedResult(join(data, ","))
-                .exercise();
-
-        withData(data)
-                .terminal(s -> s.map(Object::toString).collect(Collectors.joining(",", "[", "]")))
-                .expectedResult("[" + join(data, ",") + "]")
-                .exercise();
-
-        withData(data)
-                .terminal(s -> s.map(Object::toString)
-                                .collect(StringBuilder::new, StringBuilder::append, StringBuilder::append)
-                                .toString())
-                .expectedResult(join(data, ""))
-                .exercise();
-
-        withData(data)
-                .terminal(s -> s.map(Object::toString)
-                                .collect(() -> new StringJoiner(","),
-                                         (sj, cs) -> sj.add(cs),
-                                         (j1, j2) -> j1.merge(j2))
-                                .toString())
-                .expectedResult(join(data, ","))
-                .exercise();
-
-        withData(data)
-                .terminal(s -> s.map(Object::toString)
-                                .collect(() -> new StringJoiner(",", "[", "]"),
-                                         (sj, cs) -> sj.add(cs),
-                                         (j1, j2) -> j1.merge(j2))
-                                .toString())
-                .expectedResult("[" + join(data, ",") + "]")
-                .exercise();
-    }
-
-    private<T> String join(TestData.OfRef<T> data, String delim) {
-        StringBuilder sb = new StringBuilder();
-        boolean first = true;
-        for (T i : data) {
-            if (!first)
-                sb.append(delim);
-            sb.append(i.toString());
-            first = false;
-        }
-        return sb.toString();
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testSimpleToMap(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        Function<Integer, Integer> keyFn = i -> i * 2;
-        Function<Integer, Integer> valueFn = i -> i * 4;
-
-        List<Integer> dataAsList = Arrays.asList(data.stream().toArray(Integer[]::new));
-        Set<Integer> dataAsSet = new HashSet<>(dataAsList);
-
-        BinaryOperator<Integer> sum = Integer::sum;
-        for (BinaryOperator<Integer> op : Arrays.asList((u, v) -> u,
-                                                        (u, v) -> v,
-                                                        sum)) {
-            try {
-                exerciseMapTabulation(data, toMap(keyFn, valueFn),
-                                      new ToMapAssertion<>(keyFn, valueFn, op, HashMap.class));
-                if (dataAsList.size() != dataAsSet.size())
-                    fail("Expected ISE on input with duplicates");
-            }
-            catch (IllegalStateException e) {
-                if (dataAsList.size() == dataAsSet.size())
-                    fail("Expected no ISE on input without duplicates");
-            }
-
-            exerciseMapTabulation(data, toMap(keyFn, valueFn, op),
-                                  new ToMapAssertion<>(keyFn, valueFn, op, HashMap.class));
-
-            exerciseMapTabulation(data, toMap(keyFn, valueFn, op, TreeMap::new),
-                                  new ToMapAssertion<>(keyFn, valueFn, op, TreeMap.class));
-        }
-
-        // For concurrent maps, only use commutative merge functions
-        try {
-            exerciseMapTabulation(data, toConcurrentMap(keyFn, valueFn),
-                                  new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentHashMap.class));
-            if (dataAsList.size() != dataAsSet.size())
-                fail("Expected ISE on input with duplicates");
-        }
-        catch (IllegalStateException e) {
-            if (dataAsList.size() == dataAsSet.size())
-                fail("Expected no ISE on input without duplicates");
-        }
-
-        exerciseMapTabulation(data, toConcurrentMap(keyFn, valueFn, sum),
-                              new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentHashMap.class));
-
-        exerciseMapTabulation(data, toConcurrentMap(keyFn, valueFn, sum, ConcurrentSkipListMap::new),
-                              new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentSkipListMap.class));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testSimpleGroupBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        Function<Integer, Integer> classifier = i -> i % 3;
-
-        // Single-level groupBy
-        exerciseMapTabulation(data, groupingBy(classifier),
-                              new GroupedMapAssertion<>(classifier, HashMap.class,
-                                                        new ListAssertion<>()));
-        exerciseMapTabulation(data, groupingByConcurrent(classifier),
-                              new GroupedMapAssertion<>(classifier, ConcurrentHashMap.class,
-                                                        new ListAssertion<>()));
-
-        // With explicit constructors
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, TreeMap::new, toCollection(HashSet::new)),
-                              new GroupedMapAssertion<>(classifier, TreeMap.class,
-                                                        new CollectionAssertion<Integer>(HashSet.class, false)));
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new,
-                                                   toCollection(HashSet::new)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentSkipListMap.class,
-                                                        new CollectionAssertion<Integer>(HashSet.class, false)));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testTwoLevelGroupBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        Function<Integer, Integer> classifier = i -> i % 6;
-        Function<Integer, Integer> classifier2 = i -> i % 23;
-
-        // Two-level groupBy
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, groupingBy(classifier2)),
-                              new GroupedMapAssertion<>(classifier, HashMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, HashMap.class,
-                                                                                  new ListAssertion<>())));
-        // with concurrent as upstream
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, groupingBy(classifier2)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentHashMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, HashMap.class,
-                                                                                  new ListAssertion<>())));
-        // with concurrent as downstream
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, groupingByConcurrent(classifier2)),
-                              new GroupedMapAssertion<>(classifier, HashMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, ConcurrentHashMap.class,
-                                                                                  new ListAssertion<>())));
-        // with concurrent as upstream and downstream
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, groupingByConcurrent(classifier2)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentHashMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, ConcurrentHashMap.class,
-                                                                                  new ListAssertion<>())));
-
-        // With explicit constructors
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, TreeMap::new, groupingBy(classifier2, TreeMap::new, toCollection(HashSet::new))),
-                              new GroupedMapAssertion<>(classifier, TreeMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, TreeMap.class,
-                                                                                  new CollectionAssertion<Integer>(HashSet.class, false))));
-        // with concurrent as upstream
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, groupingBy(classifier2, TreeMap::new, toList())),
-                              new GroupedMapAssertion<>(classifier, ConcurrentSkipListMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, TreeMap.class,
-                                                                                  new ListAssertion<>())));
-        // with concurrent as downstream
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, TreeMap::new, groupingByConcurrent(classifier2, ConcurrentSkipListMap::new, toList())),
-                              new GroupedMapAssertion<>(classifier, TreeMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, ConcurrentSkipListMap.class,
-                                                                                  new ListAssertion<>())));
-        // with concurrent as upstream and downstream
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, groupingByConcurrent(classifier2, ConcurrentSkipListMap::new, toList())),
-                              new GroupedMapAssertion<>(classifier, ConcurrentSkipListMap.class,
-                                                        new GroupedMapAssertion<>(classifier2, ConcurrentSkipListMap.class,
-                                                                                  new ListAssertion<>())));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testGroupedReduce(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        Function<Integer, Integer> classifier = i -> i % 3;
-
-        // Single-level simple reduce
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, reducing(0, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, HashMap.class,
-                                                        new ReduceAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
-        // with concurrent
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, reducing(0, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentHashMap.class,
-                                                        new ReduceAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
-
-        // With explicit constructors
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, TreeMap::new, reducing(0, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, TreeMap.class,
-                                                        new ReduceAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
-        // with concurrent
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, reducing(0, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentSkipListMap.class,
-                                                        new ReduceAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
-
-        // Single-level map-reduce
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, reducing(0, mDoubler, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, HashMap.class,
-                                                        new ReduceAssertion<>(0, mDoubler, Integer::sum)));
-        // with concurrent
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, reducing(0, mDoubler, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentHashMap.class,
-                                                        new ReduceAssertion<>(0, mDoubler, Integer::sum)));
-
-        // With explicit constructors
-        exerciseMapTabulation(data,
-                              groupingBy(classifier, TreeMap::new, reducing(0, mDoubler, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, TreeMap.class,
-                                                        new ReduceAssertion<>(0, mDoubler, Integer::sum)));
-        // with concurrent
-        exerciseMapTabulation(data,
-                              groupingByConcurrent(classifier, ConcurrentSkipListMap::new, reducing(0, mDoubler, Integer::sum)),
-                              new GroupedMapAssertion<>(classifier, ConcurrentSkipListMap.class,
-                                                        new ReduceAssertion<>(0, mDoubler, Integer::sum)));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testSimplePartition(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        Predicate<Integer> classifier = i -> i % 3 == 0;
-
-        // Single-level partition to downstream List
-        exerciseMapTabulation(data,
-                              partitioningBy(classifier),
-                              new PartitionAssertion<>(classifier, new ListAssertion<>()));
-        exerciseMapTabulation(data,
-                              partitioningBy(classifier, toList()),
-                              new PartitionAssertion<>(classifier, new ListAssertion<>()));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testTwoLevelPartition(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        Predicate<Integer> classifier = i -> i % 3 == 0;
-        Predicate<Integer> classifier2 = i -> i % 7 == 0;
-
-        // Two level partition
-        exerciseMapTabulation(data,
-                              partitioningBy(classifier, partitioningBy(classifier2)),
-                              new PartitionAssertion<>(classifier,
-                                                       new PartitionAssertion(classifier2, new ListAssertion<>())));
-
-        // Two level partition with reduce
-        exerciseMapTabulation(data,
-                              partitioningBy(classifier, reducing(0, Integer::sum)),
-                              new PartitionAssertion<>(classifier,
-                                                       new ReduceAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
-    }
-
-    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
-    public void testComposeFinisher(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
-        List<Integer> asList = exerciseTerminalOps(data, s -> s.collect(toList()));
-        List<Integer> asImmutableList = exerciseTerminalOps(data, s -> s.collect(collectingAndThen(toList(), Collections::unmodifiableList)));
-        assertEquals(asList, asImmutableList);
-        try {
-            asImmutableList.add(0);
-            fail("Expecting immutable result");
-        }
-        catch (UnsupportedOperationException ignored) { }
-    }
-
-}