8019381: HashMap.isEmpty is non-final, potential issues for get/remove

Reviewed-by: chegar, mduigou

src/share/classes/java/util/HashMap.java

@@ -1013,7 +1013,7 @@ public class HashMap<K,V>
      */
     @SuppressWarnings("unchecked")
     final Entry<K,V> getEntry(Object key) {
-        if (isEmpty()) {
+        if (size == 0) {
             return null;
         }
         if (key == null) {
@@ -1468,7 +1468,7 @@ public class HashMap<K,V>
 
     @Override
     public boolean remove(Object key, Object value) {
-        if (isEmpty()) {
+        if (size == 0) {
             return false;
         }
         if (key == null) {
@@ -1531,7 +1531,7 @@ public class HashMap<K,V>
 
     @Override
     public boolean replace(K key, V oldValue, V newValue) {
-        if (isEmpty()) {
+        if (size == 0) {
             return false;
         }
         if (key == null) {
@@ -1574,7 +1574,7 @@ public class HashMap<K,V>
 
    @Override
     public V replace(K key, V value) {
-        if (isEmpty()) {
+        if (size == 0) {
             return null;
         }
         if (key == null) {
@@ -1694,7 +1694,7 @@ public class HashMap<K,V>
 
     @Override
     public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
-        if (isEmpty()) {
+        if (size == 0) {
             return null;
         }
         if (key == null) {
@@ -1980,7 +1980,7 @@ public class HashMap<K,V>
      * TreeNode in a TreeBin.
      */
     final Entry<K,V> removeEntryForKey(Object key) {
-        if (isEmpty()) {
+        if (size == 0) {
             return null;
         }
         if (key == null) {
@@ -2040,7 +2040,7 @@ public class HashMap<K,V>
      * for matching.
      */
     final Entry<K,V> removeMapping(Object o) {
-        if (isEmpty() || !(o instanceof Map.Entry))
+        if (size == 0 || !(o instanceof Map.Entry))
             return null;
 
         Map.Entry<?,?> entry = (Map.Entry<?,?>) o;

test/java/util/HashMap/OverrideIsEmpty.java

+/*
+ * Copyright (c) 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.
+ */
+
+/*
+ * Portions Copyright (c) 2013 IBM Corporation
+ */
+
+/**
+ * @test
+ * @bug 8019381
+ * @summary Verify that we do not get exception when we override isEmpty()
+ *          in a subclass of HashMap
+ * @author zhangshj@linux.vnet.ibm.com
+ */
+
+import java.util.function.BiFunction;
+import java.util.HashMap;
+
+public class OverrideIsEmpty {
+    public static class NotEmptyHashMap<K,V> extends HashMap<K,V> {
+        private K alwaysExistingKey;
+        private V alwaysExistingValue;
+
+        @Override
+        public V get(Object key) {
+            if (key == alwaysExistingKey) {
+                return alwaysExistingValue;
+            }
+            return super.get(key);
+        }
+
+        @Override
+        public int size() {
+            return super.size() + 1;
+        }
+
+        @Override
+        public boolean isEmpty() {
+            return size() == 0;
+        }
+    }
+
+    public static void main(String[] args) {
+        NotEmptyHashMap<Object, Object> map = new NotEmptyHashMap<>();
+        Object key = new Object();
+        Object value = new Object();
+        map.get(key);
+        map.remove(key);
+        map.replace(key, value, null);
+        map.replace(key, value);
+        map.computeIfPresent(key, new BiFunction<Object, Object, Object>() {
+            public Object apply(Object key, Object oldValue) {
+                return oldValue;
+            }
+        });
+    }
+}
+