changeset 25803:ab8f8e106d0a

8051991: Flatten VersionHelper hierarchies Reviewed-by: vinnie
author prappo
date Fri, 01 Aug 2014 14:57:15 +0100
parents 1dc2d3b5d4e6
children 4ae4525723a5
files jdk/src/share/classes/com/sun/jndi/ldap/VersionHelper.java jdk/src/share/classes/com/sun/jndi/ldap/VersionHelper12.java jdk/src/share/classes/com/sun/naming/internal/VersionHelper.java jdk/src/share/classes/com/sun/naming/internal/VersionHelper12.java
diffstat 4 files changed, 253 insertions(+), 416 deletions(-) [+]
line wrap: on
line diff
--- a/jdk/src/share/classes/com/sun/jndi/ldap/VersionHelper.java	Fri Aug 01 16:29:46 2014 +0400
+++ b/jdk/src/share/classes/com/sun/jndi/ldap/VersionHelper.java	Fri Aug 01 14:57:15 2014 +0100
@@ -25,32 +25,77 @@
 
 package com.sun.jndi.ldap;
 
+import sun.misc.SharedSecrets;
+
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.net.URLClassLoader;
+import java.security.AccessControlContext;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
 
-abstract class VersionHelper {
+public final class VersionHelper {
 
-    private static final VersionHelper helper = new VersionHelper12();
+    private static final VersionHelper helper = new VersionHelper();
 
-    VersionHelper() {} // Disallow anyone from creating one of these.
+    /**
+     * Determines whether classes may be loaded from an arbitrary URL code base.
+     */
+    private static final boolean trustURLCodebase;
+
+    static {
+        // System property to control whether classes may be loaded from an
+        // arbitrary URL code base
+        PrivilegedAction<String> act =
+                () -> System.getProperty("com.sun.jndi.ldap.object.trustURLCodebase", "false");
+        String trust = AccessController.doPrivileged(act);
+        trustURLCodebase = "true".equalsIgnoreCase(trust);
+    }
+
+    private VersionHelper() { }
 
     static VersionHelper getVersionHelper() {
         return helper;
     }
 
-    abstract ClassLoader getURLClassLoader(String[] url)
-        throws MalformedURLException;
+    ClassLoader getURLClassLoader(String[] url) throws MalformedURLException {
+        ClassLoader parent = getContextClassLoader();
+        /*
+         * Classes may only be loaded from an arbitrary URL code base when
+         * the system property com.sun.jndi.ldap.object.trustURLCodebase
+         * has been set to "true".
+         */
+        if (url != null && trustURLCodebase) {
+            return URLClassLoader.newInstance(getUrlArray(url), parent);
+        } else {
+            return parent;
+        }
+    }
 
+    Class<?> loadClass(String className) throws ClassNotFoundException {
+        return Class.forName(className, true, getContextClassLoader());
+    }
 
-    static protected URL[] getUrlArray(String[] url) throws MalformedURLException {
+    Thread createThread(Runnable r) {
+        AccessControlContext acc = AccessController.getContext();
+        // 4290486: doPrivileged is needed to create a thread in
+        // an environment that restricts "modifyThreadGroup".
+        PrivilegedAction<Thread> act =
+                () -> SharedSecrets.getJavaLangAccess().newThreadWithAcc(r, acc);
+        return AccessController.doPrivileged(act);
+    }
+
+    private ClassLoader getContextClassLoader() {
+        PrivilegedAction<ClassLoader> act =
+                Thread.currentThread()::getContextClassLoader;
+        return AccessController.doPrivileged(act);
+    }
+
+    private static URL[] getUrlArray(String[] url) throws MalformedURLException {
         URL[] urlArray = new URL[url.length];
         for (int i = 0; i < urlArray.length; i++) {
             urlArray[i] = new URL(url[i]);
         }
         return urlArray;
     }
-
-    abstract Class<?> loadClass(String className) throws ClassNotFoundException;
-
-    abstract Thread createThread(Runnable r);
 }
--- a/jdk/src/share/classes/com/sun/jndi/ldap/VersionHelper12.java	Fri Aug 01 16:29:46 2014 +0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,98 +0,0 @@
-/*
- * Copyright (c) 1999, 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.  Oracle designates this
- * particular file as subject to the "Classpath" exception as provided
- * by Oracle in the LICENSE file that accompanied this code.
- *
- * 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 com.sun.jndi.ldap;
-
-import java.net.URLClassLoader;
-import java.net.MalformedURLException;
-import java.security.AccessControlContext;
-import java.security.AccessController;
-import java.security.PrivilegedAction;
-import sun.misc.SharedSecrets;
-
-final class VersionHelper12 extends VersionHelper {
-
-    // System property to control whether classes may be loaded from an
-    // arbitrary URL code base.
-    private static final String TRUST_URL_CODEBASE_PROPERTY =
-        "com.sun.jndi.ldap.object.trustURLCodebase";
-
-    // Determine whether classes may be loaded from an arbitrary URL code base.
-    private static final String trustURLCodebase =
-        AccessController.doPrivileged(
-            new PrivilegedAction<String>() {
-                public String run() {
-                    return System.getProperty(TRUST_URL_CODEBASE_PROPERTY,
-                            "false");
-                }
-            }
-        );
-
-    VersionHelper12() {} // Disallow external from creating one of these.
-
-    ClassLoader getURLClassLoader(String[] url)
-        throws MalformedURLException {
-            ClassLoader parent = getContextClassLoader();
-            /*
-             * Classes may only be loaded from an arbitrary URL code base when
-             * the system property com.sun.jndi.ldap.object.trustURLCodebase
-             * has been set to "true".
-             */
-            if (url != null && "true".equalsIgnoreCase(trustURLCodebase)) {
-                return URLClassLoader.newInstance(getUrlArray(url), parent);
-            } else {
-                return parent;
-            }
-    }
-
-    Class<?> loadClass(String className) throws ClassNotFoundException {
-        ClassLoader cl = getContextClassLoader();
-        return Class.forName(className, true, cl);
-    }
-
-    private ClassLoader getContextClassLoader() {
-        return AccessController.doPrivileged(
-            new PrivilegedAction<ClassLoader>() {
-                public ClassLoader run() {
-                    return Thread.currentThread().getContextClassLoader();
-                }
-            }
-        );
-    }
-
-    Thread createThread(final Runnable r) {
-        final AccessControlContext acc = AccessController.getContext();
-        // 4290486: doPrivileged is needed to create a thread in
-        // an environment that restricts "modifyThreadGroup".
-        return AccessController.doPrivileged(
-                new PrivilegedAction<Thread>() {
-                    public Thread run() {
-                        return SharedSecrets.getJavaLangAccess()
-                                .newThreadWithAcc(r, acc);
-                    }
-                }
-        );
-    }
-}
--- a/jdk/src/share/classes/com/sun/naming/internal/VersionHelper.java	Fri Aug 01 16:29:46 2014 +0400
+++ b/jdk/src/share/classes/com/sun/naming/internal/VersionHelper.java	Fri Aug 01 14:57:15 2014 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2014, 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
@@ -25,14 +25,19 @@
 
 package com.sun.naming.internal;
 
+import javax.naming.NamingEnumeration;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
 import java.io.InputStream;
-import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URL;
-import java.util.StringTokenizer;
-import java.util.Vector;
-
-import javax.naming.NamingEnumeration;
+import java.net.URLClassLoader;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.*;
 
 /**
  * VersionHelper was used by JNDI to accommodate differences between
@@ -45,10 +50,10 @@
  * @author Scott Seligman
  */
 
-public abstract class VersionHelper {
-    private static VersionHelper helper = null;
+public final class VersionHelper {
+    private static final VersionHelper helper = new VersionHelper();
 
-    final static String[] PROPS = new String[] {
+    final static String[] PROPS = new String[]{
         javax.naming.Context.INITIAL_CONTEXT_FACTORY,
         javax.naming.Context.OBJECT_FACTORIES,
         javax.naming.Context.URL_PKG_PREFIXES,
@@ -67,31 +72,57 @@
     public final static int DNS_URL = 5;
     public final static int CONTROL_FACTORIES = 6;
 
-    VersionHelper() {} // Disallow anyone from creating one of these.
-
-    static {
-        helper = new VersionHelper12();
-    }
+    private VersionHelper() {} // Disallow anyone from creating one of these.
 
     public static VersionHelper getVersionHelper() {
         return helper;
     }
 
-    public abstract Class<?> loadClass(String className)
-        throws ClassNotFoundException;
+    public Class<?> loadClass(String className) throws ClassNotFoundException {
+        return loadClass(className, getContextClassLoader());
+    }
 
-    abstract Class<?> loadClass(String className, ClassLoader cl)
-        throws ClassNotFoundException;
+    /**
+     * @param className A non-null fully qualified class name.
+     * @param codebase  A non-null, space-separated list of URL strings.
+     */
+    public Class<?> loadClass(String className, String codebase)
+            throws ClassNotFoundException, MalformedURLException {
 
-    public abstract Class<?> loadClass(String className, String codebase)
-        throws ClassNotFoundException, MalformedURLException;
+        ClassLoader parent = getContextClassLoader();
+        ClassLoader cl =
+                URLClassLoader.newInstance(getUrlArray(codebase), parent);
+
+        return loadClass(className, cl);
+    }
+
+    /**
+     * Package private.
+     * <p>
+     * This internal method is used with Thread Context Class Loader (TCCL),
+     * please don't expose this method as public.
+     */
+    Class<?> loadClass(String className, ClassLoader cl)
+            throws ClassNotFoundException {
+        Class<?> cls = Class.forName(className, true, cl);
+        return cls;
+    }
 
     /*
-     * Returns a JNDI property from the system properties.  Returns
+     * Returns a JNDI property from the system properties. Returns
      * null if the property is not set, or if there is no permission
      * to read it.
      */
-    abstract String getJndiProperty(int i);
+    String getJndiProperty(int i) {
+        PrivilegedAction<String> act = () -> {
+            try {
+                return System.getProperty(PROPS[i]);
+            } catch (SecurityException e) {
+                return null;
+            }
+        };
+        return AccessController.doPrivileged(act);
+    }
 
     /*
      * Reads each property in PROPS from the system properties, and
@@ -99,13 +130,33 @@
      * unset property, the corresponding array element is set to null.
      * Returns null if there is no permission to call System.getProperties().
      */
-    abstract String[] getJndiProperties();
+    String[] getJndiProperties() {
+        PrivilegedAction<Properties> act = () -> {
+            try {
+                return System.getProperties();
+            } catch (SecurityException e) {
+                return null;
+            }
+        };
+        Properties sysProps = AccessController.doPrivileged(act);
+        if (sysProps == null) {
+            return null;
+        }
+        String[] jProps = new String[PROPS.length];
+        for (int i = 0; i < PROPS.length; i++) {
+            jProps[i] = sysProps.getProperty(PROPS[i]);
+        }
+        return jProps;
+    }
 
     /*
      * Returns the resource of a given name associated with a particular
      * class (never null), or null if none can be found.
      */
-    abstract InputStream getResourceAsStream(Class<?> c, String name);
+    InputStream getResourceAsStream(Class<?> c, String name) {
+        PrivilegedAction<InputStream> act = () -> c.getResourceAsStream(name);
+        return AccessController.doPrivileged(act);
+    }
 
     /*
      * Returns an input stream for a file in <java.home>/lib,
@@ -113,7 +164,22 @@
      *
      * @param filename  The file name, sans directory.
      */
-    abstract InputStream getJavaHomeLibStream(String filename);
+    InputStream getJavaHomeLibStream(String filename) {
+        PrivilegedAction<InputStream> act = () -> {
+            try {
+                String javahome = System.getProperty("java.home");
+                if (javahome == null) {
+                    return null;
+                }
+                String pathname = javahome + File.separator +
+                        "lib" + File.separator + filename;
+                return new FileInputStream(pathname);
+            } catch (Exception e) {
+                return null;
+            }
+        };
+        return AccessController.doPrivileged(act);
+    }
 
     /*
      * Returns an enumeration (never null) of InputStreams of the
@@ -121,29 +187,55 @@
      * loader.  Null represents the bootstrap class loader in some
      * Java implementations.
      */
-    abstract NamingEnumeration<InputStream> getResources(
-            ClassLoader cl, String name)
-        throws IOException;
+    NamingEnumeration<InputStream> getResources(ClassLoader cl,
+                                                String name) throws IOException {
+        Enumeration<URL> urls;
+        PrivilegedExceptionAction<Enumeration<URL>> act = () ->
+                (cl == null)
+                        ? ClassLoader.getSystemResources(name)
+                        : cl.getResources(name);
+        try {
+            urls = AccessController.doPrivileged(act);
+        } catch (PrivilegedActionException e) {
+            throw (IOException) e.getException();
+        }
+        return new InputStreamEnumeration(urls);
+    }
 
-    /*
-     * Returns the context class loader associated with the current thread.
-     * Null indicates the bootstrap class loader in some Java implementations.
-     *
-     * @throws SecurityException if the class loader is not accessible.
+
+    /**
+     * Package private.
+     * <p>
+     * This internal method returns Thread Context Class Loader (TCCL),
+     * if null, returns the system Class Loader.
+     * <p>
+     * Please don't expose this method as public.
+     * @throws SecurityException if the class loader is not accessible
      */
-    abstract ClassLoader getContextClassLoader();
+    ClassLoader getContextClassLoader() {
 
-    static protected URL[] getUrlArray(String codebase)
-        throws MalformedURLException {
+        PrivilegedAction<ClassLoader> act = () -> {
+            ClassLoader loader = Thread.currentThread().getContextClassLoader();
+            if (loader == null) {
+                // Don't use bootstrap class loader directly!
+                loader = ClassLoader.getSystemClassLoader();
+            }
+            return loader;
+        };
+        return AccessController.doPrivileged(act);
+    }
+
+    private static URL[] getUrlArray(String codebase)
+            throws MalformedURLException {
         // Parse codebase into separate URLs
         StringTokenizer parser = new StringTokenizer(codebase);
-        Vector<String> vec = new Vector<>(10);
+        List<String> list = new ArrayList<>();
         while (parser.hasMoreTokens()) {
-            vec.addElement(parser.nextToken());
+            list.add(parser.nextToken());
         }
-        String[] url = new String[vec.size()];
+        String[] url = new String[list.size()];
         for (int i = 0; i < url.length; i++) {
-            url[i] = vec.elementAt(i);
+            url[i] = list.get(i);
         }
 
         URL[] urlArray = new URL[url.length];
@@ -152,4 +244,70 @@
         }
         return urlArray;
     }
+
+    /**
+     * Given an enumeration of URLs, an instance of this class represents
+     * an enumeration of their InputStreams.  Each operation on the URL
+     * enumeration is performed within a doPrivileged block.
+     * This is used to enumerate the resources under a foreign codebase.
+     * This class is not MT-safe.
+     */
+    private class InputStreamEnumeration implements
+            NamingEnumeration<InputStream> {
+
+        private final Enumeration<URL> urls;
+
+        private InputStream nextElement;
+
+        InputStreamEnumeration(Enumeration<URL> urls) {
+            this.urls = urls;
+        }
+
+        /*
+         * Returns the next InputStream, or null if there are no more.
+         * An InputStream that cannot be opened is skipped.
+         */
+        private InputStream getNextElement() {
+            PrivilegedAction<InputStream> act = () -> {
+                while (urls.hasMoreElements()) {
+                    try {
+                        return urls.nextElement().openStream();
+                    } catch (IOException e) {
+                        // skip this URL
+                    }
+                }
+                return null;
+            };
+            return AccessController.doPrivileged(act);
+        }
+
+        public boolean hasMore() {
+            if (nextElement != null) {
+                return true;
+            }
+            nextElement = getNextElement();
+            return (nextElement != null);
+        }
+
+        public boolean hasMoreElements() {
+            return hasMore();
+        }
+
+        public InputStream next() {
+            if (hasMore()) {
+                InputStream res = nextElement;
+                nextElement = null;
+                return res;
+            } else {
+                throw new NoSuchElementException();
+            }
+        }
+
+        public InputStream nextElement() {
+            return next();
+        }
+
+        public void close() {
+        }
+    }
 }
--- a/jdk/src/share/classes/com/sun/naming/internal/VersionHelper12.java	Fri Aug 01 16:29:46 2014 +0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,268 +0,0 @@
-/*
- * Copyright (c) 1999, 2011, 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.  Oracle designates this
- * particular file as subject to the "Classpath" exception as provided
- * by Oracle in the LICENSE file that accompanied this code.
- *
- * 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 com.sun.naming.internal;
-
-import java.io.InputStream;
-import java.io.IOException;
-import java.net.MalformedURLException;
-import java.net.URLClassLoader;
-import java.net.URL;
-import java.security.AccessController;
-import java.security.PrivilegedAction;
-import java.security.PrivilegedActionException;
-import java.security.PrivilegedExceptionAction;
-import java.util.Enumeration;
-import java.util.NoSuchElementException;
-import java.util.Properties;
-
-import javax.naming.*;
-
-/**
- * VersionHelper was used by JNDI to accommodate differences between
- * JDK 1.1.x and the Java 2 platform. As this is no longer necessary
- * since JNDI's inclusion in the platform, this class currently
- * serves as a set of utilities for performing system-level things,
- * such as class-loading and reading system properties.
- *
- * @author Rosanna Lee
- * @author Scott Seligman
- */
-
-final class VersionHelper12 extends VersionHelper {
-
-    // Disallow external from creating one of these.
-    VersionHelper12() {
-    }
-
-    public Class<?> loadClass(String className) throws ClassNotFoundException {
-        return loadClass(className, getContextClassLoader());
-    }
-
-    /**
-     * Package private.
-     *
-     * This internal method is used with Thread Context Class Loader (TCCL),
-     * please don't expose this method as public.
-     */
-    Class<?> loadClass(String className, ClassLoader cl)
-        throws ClassNotFoundException {
-        Class<?> cls = Class.forName(className, true, cl);
-        return cls;
-    }
-
-    /**
-     * @param className A non-null fully qualified class name.
-     * @param codebase A non-null, space-separated list of URL strings.
-     */
-    public Class<?> loadClass(String className, String codebase)
-            throws ClassNotFoundException, MalformedURLException {
-
-        ClassLoader parent = getContextClassLoader();
-        ClassLoader cl =
-                 URLClassLoader.newInstance(getUrlArray(codebase), parent);
-
-        return loadClass(className, cl);
-    }
-
-    String getJndiProperty(final int i) {
-        return AccessController.doPrivileged(
-            new PrivilegedAction<String>() {
-                public String run() {
-                    try {
-                        return System.getProperty(PROPS[i]);
-                    } catch (SecurityException e) {
-                        return null;
-                    }
-                }
-            }
-        );
-    }
-
-    String[] getJndiProperties() {
-        Properties sysProps = AccessController.doPrivileged(
-            new PrivilegedAction<Properties>() {
-                public Properties run() {
-                    try {
-                        return System.getProperties();
-                    } catch (SecurityException e) {
-                        return null;
-                    }
-                }
-            }
-        );
-        if (sysProps == null) {
-            return null;
-        }
-        String[] jProps = new String[PROPS.length];
-        for (int i = 0; i < PROPS.length; i++) {
-            jProps[i] = sysProps.getProperty(PROPS[i]);
-        }
-        return jProps;
-    }
-
-    InputStream getResourceAsStream(final Class<?> c, final String name) {
-        return AccessController.doPrivileged(
-            new PrivilegedAction<InputStream>() {
-                public InputStream run() {
-                    return c.getResourceAsStream(name);
-                }
-            }
-        );
-    }
-
-    InputStream getJavaHomeLibStream(final String filename) {
-        return AccessController.doPrivileged(
-            new PrivilegedAction<InputStream>() {
-                public InputStream run() {
-                    try {
-                        String javahome = System.getProperty("java.home");
-                        if (javahome == null) {
-                            return null;
-                        }
-                        String pathname = javahome + java.io.File.separator +
-                            "lib" + java.io.File.separator + filename;
-                        return new java.io.FileInputStream(pathname);
-                    } catch (Exception e) {
-                        return null;
-                    }
-                }
-            }
-        );
-    }
-
-    NamingEnumeration<InputStream> getResources(final ClassLoader cl,
-            final String name) throws IOException {
-        Enumeration<URL> urls;
-        try {
-            urls = AccessController.doPrivileged(
-                new PrivilegedExceptionAction<Enumeration<URL>>() {
-                    public Enumeration<URL> run() throws IOException {
-                        return (cl == null)
-                            ? ClassLoader.getSystemResources(name)
-                            : cl.getResources(name);
-                    }
-                }
-            );
-        } catch (PrivilegedActionException e) {
-            throw (IOException)e.getException();
-        }
-        return new InputStreamEnumeration(urls);
-    }
-
-    /**
-     * Package private.
-     *
-     * This internal method returns Thread Context Class Loader (TCCL),
-     * if null, returns the system Class Loader.
-     *
-     * Please don't expose this method as public.
-     */
-    ClassLoader getContextClassLoader() {
-
-        return AccessController.doPrivileged(
-            new PrivilegedAction<ClassLoader>() {
-                public ClassLoader run() {
-                    ClassLoader loader =
-                            Thread.currentThread().getContextClassLoader();
-                    if (loader == null) {
-                        // Don't use bootstrap class loader directly!
-                        loader = ClassLoader.getSystemClassLoader();
-                    }
-
-                    return loader;
-                }
-            }
-        );
-    }
-
-    /**
-     * Given an enumeration of URLs, an instance of this class represents
-     * an enumeration of their InputStreams.  Each operation on the URL
-     * enumeration is performed within a doPrivileged block.
-     * This is used to enumerate the resources under a foreign codebase.
-     * This class is not MT-safe.
-     */
-    class InputStreamEnumeration implements NamingEnumeration<InputStream> {
-
-        private final Enumeration<URL> urls;
-
-        private InputStream nextElement = null;
-
-        InputStreamEnumeration(Enumeration<URL> urls) {
-            this.urls = urls;
-        }
-
-        /*
-         * Returns the next InputStream, or null if there are no more.
-         * An InputStream that cannot be opened is skipped.
-         */
-        private InputStream getNextElement() {
-            return AccessController.doPrivileged(
-                new PrivilegedAction<InputStream>() {
-                    public InputStream run() {
-                        while (urls.hasMoreElements()) {
-                            try {
-                                return urls.nextElement().openStream();
-                            } catch (IOException e) {
-                                // skip this URL
-                            }
-                        }
-                        return null;
-                    }
-                }
-            );
-        }
-
-        public boolean hasMore() {
-            if (nextElement != null) {
-                return true;
-            }
-            nextElement = getNextElement();
-            return (nextElement != null);
-        }
-
-        public boolean hasMoreElements() {
-            return hasMore();
-        }
-
-        public InputStream next() {
-            if (hasMore()) {
-                InputStream res = nextElement;
-                nextElement = null;
-                return res;
-            } else {
-                throw new NoSuchElementException();
-            }
-        }
-
-        public InputStream nextElement() {
-            return next();
-        }
-
-        public void close() {
-        }
-    }
-}