6312706: Map entrySet iterators should return different entries on each call to next()

Reviewed-by: mduigou, alanb
Contributed-by: NNeil Richards <neil.richards@ngmr.net>

src/share/classes/java/util/EnumMap.java

@@ -106,7 +106,7 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
     /**
      * Distinguished non-null value for representing null values.
      */
-    private static final Object NULL = new Object();
+    private static final Object NULL = new Integer(0);
 
     private Object maskNull(Object value) {
         return (value == null ? NULL : value);
@@ -116,7 +116,7 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
         return (V) (value == NULL ? null : value);
     }
 
-    private static Enum[] ZERO_LENGTH_ENUM_ARRAY = new Enum[0];
+    private static final Enum[] ZERO_LENGTH_ENUM_ARRAY = new Enum[0];
 
     /**
      * Creates an empty enum map with the specified key type.
@@ -464,6 +464,7 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
         public Iterator<Map.Entry<K,V>> iterator() {
             return new EntryIterator();
         }
+
         public boolean contains(Object o) {
             if (!(o instanceof Map.Entry))
                 return false;
@@ -552,70 +553,82 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
         }
     }
 
-    /**
-     * Since we don't use Entry objects, we use the Iterator itself as entry.
-     */
-    private class EntryIterator extends EnumMapIterator<Map.Entry<K,V>>
-        implements Map.Entry<K,V>
-    {
+    private class EntryIterator extends EnumMapIterator<Map.Entry<K,V>> {
+        private Entry lastReturnedEntry = null;
+
         public Map.Entry<K,V> next() {
             if (!hasNext())
                 throw new NoSuchElementException();
-            lastReturnedIndex = index++;
-            return this;
+            lastReturnedEntry = new Entry(index++);
+            return lastReturnedEntry;
         }
 
-        public K getKey() {
-            checkLastReturnedIndexForEntryUse();
-            return keyUniverse[lastReturnedIndex];
+        public void remove() {
+            lastReturnedIndex =
+                ((null == lastReturnedEntry) ? -1 : lastReturnedEntry.index);
+            super.remove();
+            lastReturnedEntry.index = lastReturnedIndex;
+            lastReturnedEntry = null;
         }
 
-        public V getValue() {
-            checkLastReturnedIndexForEntryUse();
-            return unmaskNull(vals[lastReturnedIndex]);
-        }
+        private class Entry implements Map.Entry<K,V> {
+            private int index;
 
-        public V setValue(V value) {
-            checkLastReturnedIndexForEntryUse();
-            V oldValue = unmaskNull(vals[lastReturnedIndex]);
-            vals[lastReturnedIndex] = maskNull(value);
-            return oldValue;
-        }
+            private Entry(int index) {
+                this.index = index;
+            }
 
-        public boolean equals(Object o) {
-            if (lastReturnedIndex < 0)
-                return o == this;
+            public K getKey() {
+                checkIndexForEntryUse();
+                return keyUniverse[index];
+            }
 
-            if (!(o instanceof Map.Entry))
-                return false;
-            Map.Entry e = (Map.Entry)o;
-            V ourValue = unmaskNull(vals[lastReturnedIndex]);
-            Object hisValue = e.getValue();
-            return e.getKey() == keyUniverse[lastReturnedIndex] &&
-                (ourValue == hisValue ||
-                 (ourValue != null && ourValue.equals(hisValue)));
-        }
+            public V getValue() {
+                checkIndexForEntryUse();
+                return unmaskNull(vals[index]);
+            }
 
-        public int hashCode() {
-            if (lastReturnedIndex < 0)
-                return super.hashCode();
+            public V setValue(V value) {
+                checkIndexForEntryUse();
+                V oldValue = unmaskNull(vals[index]);
+                vals[index] = maskNull(value);
+                return oldValue;
+            }
 
-            Object value = vals[lastReturnedIndex];
-            return keyUniverse[lastReturnedIndex].hashCode()
-                ^ (value == NULL ? 0 : value.hashCode());
-        }
+            public boolean equals(Object o) {
+                if (index < 0)
+                    return o == this;
 
-        public String toString() {
-            if (lastReturnedIndex < 0)
-                return super.toString();
+                if (!(o instanceof Map.Entry))
+                    return false;
 
-            return keyUniverse[lastReturnedIndex] + "="
-                + unmaskNull(vals[lastReturnedIndex]);
-        }
+                Map.Entry e = (Map.Entry)o;
+                V ourValue = unmaskNull(vals[index]);
+                Object hisValue = e.getValue();
+                return (e.getKey() == keyUniverse[index] &&
+                        (ourValue == hisValue ||
+                         (ourValue != null && ourValue.equals(hisValue))));
+            }
 
-        private void checkLastReturnedIndexForEntryUse() {
-            if (lastReturnedIndex < 0)
-                throw new IllegalStateException("Entry was removed");
+            public int hashCode() {
+                if (index < 0)
+                    return super.hashCode();
+
+                return entryHashCode(index);
+            }
+
+            public String toString() {
+                if (index < 0)
+                    return super.toString();
+
+                return keyUniverse[index] + "="
+                    + unmaskNull(vals[index]);
+            }
+
+            private void checkIndexForEntryUse() {
+                if (index < 0)
+                    throw new IllegalStateException("Entry was removed");
+            }
         }
     }
 
@@ -631,10 +644,35 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
      * @return <tt>true</tt> if the specified object is equal to this map
      */
     public boolean equals(Object o) {
-        if (!(o instanceof EnumMap))
-            return super.equals(o);
+        if (this == o)
+            return true;
+        if (o instanceof EnumMap)
+            return equals((EnumMap)o);
+        if (!(o instanceof Map))
+            return false;
+
+        Map<K,V> m = (Map<K,V>)o;
+        if (size != m.size())
+            return false;
+
+        for (int i = 0; i < keyUniverse.length; i++) {
+            if (null != vals[i]) {
+                K key = keyUniverse[i];
+                V value = unmaskNull(vals[i]);
+                if (null == value) {
+                    if (!((null == m.get(key)) && m.containsKey(key)))
+                       return false;
+                } else {
+                   if (!value.equals(m.get(key)))
+                      return false;
+                }
+            }
+        }
+
+        return true;
+    }
 
-        EnumMap em = (EnumMap)o;
+    private boolean equals(EnumMap em) {
         if (em.keyType != keyType)
             return size == 0 && em.size == 0;
 
@@ -649,6 +687,26 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
         return true;
     }
 
+    /**
+     * Returns the hash code value for this map.  The hash code of a map is
+     * defined to be the sum of the hash codes of each entry in the map.
+     */
+    public int hashCode() {
+        int h = 0;
+
+        for (int i = 0; i < keyUniverse.length; i++) {
+            if (null != vals[i]) {
+                h += entryHashCode(i);
+            }
+        }
+
+        return h;
+    }
+
+    private int entryHashCode(int index) {
+        return (keyUniverse[index].hashCode() ^ vals[index].hashCode());
+    }
+
     /**
      * Returns a shallow copy of this enum map.  (The values themselves
      * are not cloned.
@@ -705,9 +763,13 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
         s.writeInt(size);
 
         // Write out keys and values (alternating)
-        for (Map.Entry<K,V> e :  entrySet()) {
-            s.writeObject(e.getKey());
-            s.writeObject(e.getValue());
+        int entriesToBeWritten = size;
+        for (int i = 0; entriesToBeWritten > 0; i++) {
+            if (null != vals[i]) {
+                s.writeObject(keyUniverse[i]);
+                s.writeObject(unmaskNull(vals[i]));
+                entriesToBeWritten--;
+            }
         }
     }
 

src/share/classes/java/util/IdentityHashMap.java

 /*
- * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 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
@@ -829,71 +829,82 @@ public class IdentityHashMap<K,V>
         }
     }
 
-    /**
-     * Since we don't use Entry objects, we use the Iterator
-     * itself as an entry.
-     */
     private class EntryIterator
         extends IdentityHashMapIterator<Map.Entry<K,V>>
-        implements Map.Entry<K,V>
     {
+        private Entry lastReturnedEntry = null;
+
         public Map.Entry<K,V> next() {
-            nextIndex();
-            return this;
+            lastReturnedEntry = new Entry(nextIndex());
+            return lastReturnedEntry;
         }
 
-        public K getKey() {
-            // Provide a better exception than out of bounds index
-            if (lastReturnedIndex < 0)
-                throw new IllegalStateException("Entry was removed");
-
-            return (K) unmaskNull(traversalTable[lastReturnedIndex]);
+        public void remove() {
+            lastReturnedIndex =
+                ((null == lastReturnedEntry) ? -1 : lastReturnedEntry.index);
+            super.remove();
+            lastReturnedEntry.index = lastReturnedIndex;
+            lastReturnedEntry = null;
         }
 
-        public V getValue() {
-            // Provide a better exception than out of bounds index
-            if (lastReturnedIndex < 0)
-                throw new IllegalStateException("Entry was removed");
+        private class Entry implements Map.Entry<K,V> {
+            private int index;
 
-            return (V) traversalTable[lastReturnedIndex+1];
-        }
+            private Entry(int index) {
+                this.index = index;
+            }
 
-        public V setValue(V value) {
-            // It would be mean-spirited to proceed here if remove() called
-            if (lastReturnedIndex < 0)
-                throw new IllegalStateException("Entry was removed");
-            V oldValue = (V) traversalTable[lastReturnedIndex+1];
-            traversalTable[lastReturnedIndex+1] = value;
-            // if shadowing, force into main table
-            if (traversalTable != IdentityHashMap.this.table)
-                put((K) traversalTable[lastReturnedIndex], value);
-            return oldValue;
-        }
+            public K getKey() {
+                checkIndexForEntryUse();
+                return (K) unmaskNull(traversalTable[index]);
+            }
 
-        public boolean equals(Object o) {
-            if (lastReturnedIndex < 0)
-                return super.equals(o);
+            public V getValue() {
+                checkIndexForEntryUse();
+                return (V) traversalTable[index+1];
+            }
 
-            if (!(o instanceof Map.Entry))
-                return false;
-            Map.Entry e = (Map.Entry)o;
-            return e.getKey()   == getKey() &&
-                   e.getValue() == getValue();
-        }
+            public V setValue(V value) {
+                checkIndexForEntryUse();
+                V oldValue = (V) traversalTable[index+1];
+                traversalTable[index+1] = value;
+                // if shadowing, force into main table
+                if (traversalTable != IdentityHashMap.this.table)
+                    put((K) traversalTable[index], value);
+                return oldValue;
+            }
 
-        public int hashCode() {
-            if (lastReturnedIndex < 0)
-                return super.hashCode();
+            public boolean equals(Object o) {
+                if (index < 0)
+                    return super.equals(o);
 
-            return System.identityHashCode(getKey()) ^
-                   System.identityHashCode(getValue());
-        }
+                if (!(o instanceof Map.Entry))
+                    return false;
+                Map.Entry e = (Map.Entry)o;
+                return (e.getKey() == unmaskNull(traversalTable[index]) &&
+                       e.getValue() == traversalTable[index+1]);
+            }
 
-        public String toString() {
-            if (lastReturnedIndex < 0)
-                return super.toString();
+            public int hashCode() {
+                if (lastReturnedIndex < 0)
+                    return super.hashCode();
 
-            return getKey() + "=" + getValue();
+                return (System.identityHashCode(unmaskNull(traversalTable[index])) ^
+                       System.identityHashCode(traversalTable[index+1]));
+            }
+
+            public String toString() {
+                if (index < 0)
+                    return super.toString();
+
+                return (unmaskNull(traversalTable[index]) + "="
+                        + traversalTable[index+1]);
+            }
+
+            private void checkIndexForEntryUse() {
+                if (index < 0)
+                    throw new IllegalStateException("Entry was removed");
+            }
         }
     }
 

test/java/util/EnumMap/DistinctEntrySetElements.java

+/*
+ * Copyright (c) 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.
+ *
+ * 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 6312706
+ * @summary Sets from Map.entrySet() return distinct objects for each Entry
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.EnumMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class DistinctEntrySetElements {
+    static enum TestEnum { e00, e01, e02 }
+
+    public static void main(String[] args) throws Exception {
+        final EnumMap<TestEnum, String> enumMap = new EnumMap<>(TestEnum.class);
+
+        for (TestEnum e : TestEnum.values()) {
+            enumMap.put(e, e.name());
+        }
+
+        Set<Map.Entry<TestEnum, String>> entrySet = enumMap.entrySet();
+        HashSet<Map.Entry<TestEnum, String>> hashSet = new HashSet<>(entrySet);
+
+        if (false == hashSet.equals(entrySet)) {
+            throw new RuntimeException("Test FAILED: Sets are not equal.");
+        }
+        if (hashSet.hashCode() != entrySet.hashCode()) {
+            throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
+        }
+    }
+}

test/java/util/EnumMap/EntrySetIteratorRemoveInvalidatesEntry.java

+/*
+ * Copyright (c) 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.
+ *
+ * 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 6312706
+ * @summary Iterator.remove() from Map.entrySet().iterator() invalidates returned Entry.
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.EnumMap;
+import java.util.Iterator;
+import java.util.Map;
+
+public class EntrySetIteratorRemoveInvalidatesEntry {
+    static enum TestEnum { e00, e01, e02 }
+
+    public static void main(String[] args) throws Exception {
+        final EnumMap<TestEnum, String> enumMap = new EnumMap<>(TestEnum.class);
+
+        for (TestEnum e : TestEnum.values()) {
+            enumMap.put(e, e.name());
+        }
+
+        Iterator<Map.Entry<TestEnum, String>> entrySetIterator =
+            enumMap.entrySet().iterator();
+        Map.Entry<TestEnum, String> entry = entrySetIterator.next();
+
+        entrySetIterator.remove();
+
+        try {
+            entry.getKey();
+            throw new RuntimeException("Test FAILED: Entry not invalidated by removal.");
+        } catch (Exception e) { }
+    }
+}

test/java/util/EnumMap/SimpleSerialization.java

+/*
+ * Copyright (c) 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.
+ *
+ * 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 6312706
+ * @summary A serialized EnumMap can be successfully de-serialized.
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.EnumMap;
+
+public class SimpleSerialization {
+    private enum TestEnum { e00, e01, e02, e03, e04, e05, e06, e07 }
+    public static void main(final String[] args) throws Exception {
+        final EnumMap<TestEnum, String> enumMap = new EnumMap<>(TestEnum.class);
+
+        enumMap.put(TestEnum.e01, TestEnum.e01.name());
+        enumMap.put(TestEnum.e04, TestEnum.e04.name());
+        enumMap.put(TestEnum.e05, TestEnum.e05.name());
+
+        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        final ObjectOutputStream oos = new ObjectOutputStream(baos);
+
+        oos.writeObject(enumMap);
+        oos.close();
+
+        final byte[] data = baos.toByteArray();
+        final ByteArrayInputStream bais = new ByteArrayInputStream(data);
+        final ObjectInputStream ois = new ObjectInputStream(bais);
+
+        final Object deserializedObject = ois.readObject();
+        ois.close();
+
+        if (false == enumMap.equals(deserializedObject)) {
+            throw new RuntimeException(getFailureText(enumMap, deserializedObject));
+        }
+    }
+
+    private static String getFailureText(final Object orig, final Object copy) {
+        final StringWriter sw = new StringWriter();
+        final PrintWriter pw = new PrintWriter(sw);
+
+        pw.println("Test FAILED: Deserialized object is not equal to the original object");
+        pw.print("\tOriginal: ");
+        printObject(pw, orig).println();
+        pw.print("\tCopy:     ");
+        printObject(pw, copy).println();
+
+        pw.close();
+        return sw.toString();
+    }
+
+    private static PrintWriter printObject(final PrintWriter pw, final Object o) {
+        pw.printf("%s@%08x", o.getClass().getName(), System.identityHashCode(o));
+        return pw;
+    }
+}

test/java/util/IdentityHashMap/DistinctEntrySetElements.java

+/*
+ * Copyright (c) 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.
+ *
+ * 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 6312706
+ * @summary Sets from Map.entrySet() return distinct objects for each Entry
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.IdentityHashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class DistinctEntrySetElements {
+    public static void main(String[] args) throws Exception {
+        final IdentityHashMap<String, String> identityHashMap =
+            new IdentityHashMap<>();
+
+        identityHashMap.put("One", "Un");
+        identityHashMap.put("Two", "Deux");
+        identityHashMap.put("Three", "Trois");
+
+        Set<Map.Entry<String, String>> entrySet = identityHashMap.entrySet();
+        HashSet<Map.Entry<String, String>> hashSet = new HashSet<>(entrySet);
+
+        // NB: These comparisons are valid in this case because none of the
+        //     keys put into 'identityHashMap' above are equal to any other.
+        if (false == hashSet.equals(entrySet)) {
+            throw new RuntimeException("Test FAILED: Sets are not equal.");
+        }
+        if (hashSet.hashCode() != entrySet.hashCode()) {
+            throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
+        }
+    }
+}

test/java/util/IdentityHashMap/EntrySetIteratorRemoveInvalidatesEntry.java

+/*
+ * Copyright (c) 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.
+ *
+ * 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 6312706
+ * @summary Iterator.remove() from Map.entrySet().iterator() invalidates returned Entry.
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.IdentityHashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+public class EntrySetIteratorRemoveInvalidatesEntry {
+    public static void main(String[] args) throws Exception {
+        final IdentityHashMap<String, String> identityHashMap =
+            new IdentityHashMap<>();
+
+        identityHashMap.put("One", "Un");
+        identityHashMap.put("Two", "Deux");
+        identityHashMap.put("Three", "Trois");
+
+        Iterator<Map.Entry<String, String>> entrySetIterator =
+            identityHashMap.entrySet().iterator();
+        Map.Entry<String, String> entry = entrySetIterator.next();
+
+        entrySetIterator.remove();
+
+        try {
+            entry.getKey();
+            throw new RuntimeException("Test FAILED: Entry not invalidated by removal.");
+        } catch (Exception e) { }
+    }
+}

test/java/util/concurrent/ConcurrentHashMap/DistinctEntrySetElements.java

+/*
+ * Copyright (c) 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.
+ *
+ * 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 6312706
+ * @summary Sets from Map.entrySet() return distinct objects for each Entry
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class DistinctEntrySetElements {
+    public static void main(String[] args) throws Exception {
+        final ConcurrentHashMap<String, String> concurrentHashMap =
+            new ConcurrentHashMap<>();
+
+        concurrentHashMap.put("One", "Un");
+        concurrentHashMap.put("Two", "Deux");
+        concurrentHashMap.put("Three", "Trois");
+
+        Set<Map.Entry<String, String>> entrySet = concurrentHashMap.entrySet();
+        HashSet<Map.Entry<String, String>> hashSet = new HashSet<>(entrySet);
+
+        if (false == hashSet.equals(entrySet)) {
+            throw new RuntimeException("Test FAILED: Sets are not equal.");
+        }
+        if (hashSet.hashCode() != entrySet.hashCode()) {
+            throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
+        }
+    }
+}