8000955: Hashtable.Entry.hashCode() does not conform to Map.Entry.hashCode() defined behaviour

Reviewed-by: mduigou, alanb

jdk/src/share/classes/java/util/Hashtable.java

@@ -1059,7 +1059,7 @@ public class Hashtable<K,V>
         }
 
         public int hashCode() {
-            return hash ^ (value==null ? 0 : value.hashCode());
+            return (Objects.hashCode(key) ^ Objects.hashCode(value));
         }
 
         public String toString() {

jdk/test/java/util/Map/EntryHashCode.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2012 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) 2012 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 8000955
+ * @summary Map.Entry implementations need to comply with Map.Entry.hashCode() defined behaviour.
+ * @author ngmr
+ */
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentSkipListMap;
+
+public class EntryHashCode {
+    private static final int TEST_SIZE = 100;
+
+    static final Object[][] entryData = {
+        new Object[TEST_SIZE],
+        new Object[TEST_SIZE]
+    };
+
+    @SuppressWarnings("unchecked")
+    static final Map<Object,Object>[] maps = (Map<Object,Object>[])new Map[] {
+        new HashMap<>(),
+        new Hashtable<>(),
+        new IdentityHashMap<>(),
+        new LinkedHashMap<>(),
+        new TreeMap<>(),
+        new WeakHashMap<>(),
+        new ConcurrentHashMap<>(),
+        new ConcurrentSkipListMap<>()
+    };
+
+    static {
+        for (int i = 0; i < entryData[0].length; i++) {
+            // key objects need to be Comparable for use in TreeMap
+            entryData[0][i] = new Comparable<Object>() {
+                public int compareTo(Object o) {
+                    return (hashCode() - o.hashCode());
+                }
+            };
+            entryData[1][i] = new Object();
+        }
+    }
+
+    private static void addTestData(Map<Object,Object> map) {
+        for (int i = 0; i < entryData[0].length; i++) {
+            map.put(entryData[0][i], entryData[1][i]);
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        Exception failure = null;
+        for (Map<Object,Object> map: maps) {
+            addTestData(map);
+
+            try {
+                for (Map.Entry<Object,Object> e: map.entrySet()) {
+                    Object key = e.getKey();
+                    Object value = e.getValue();
+                    int expectedEntryHashCode =
+                        (Objects.hashCode(key) ^ Objects.hashCode(value));
+
+                    if (e.hashCode() != expectedEntryHashCode) {
+                        throw new Exception("FAILURE: " +
+                                e.getClass().getName() +
+                                ".hashCode() does not conform to defined" +
+                                " behaviour of java.util.Map.Entry.hashCode()");
+                    }
+                }
+            } catch (Exception e) {
+                if (failure == null) {
+                    failure = e;
+                } else {
+                    failure.addSuppressed(e);
+                }
+            } finally {
+                map.clear();
+            }
+        }
+        if (failure != null) {
+            throw failure;
+        }
+    }
+}