--- old/src/share/classes/java/util/concurrent/ConcurrentMap.java	2013-10-03 20:30:27.595126376 -0700
+++ new/src/share/classes/java/util/concurrent/ConcurrentMap.java	2013-10-03 20:30:27.439126368 -0700
@@ -195,6 +195,39 @@
      * <strong>must</strong> override this default implementation.
      */
     @Override
+    default V merge(K key, V value,
+            BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+        Objects.requireNonNull(remappingFunction);
+        Objects.requireNonNull(value);
+        V oldValue = get(key);
+        for (;;) {
+            if (oldValue != null) {
+                V newValue = remappingFunction.apply(oldValue, value);
+                if (newValue != null) {
+                    if (replace(key, oldValue, newValue))
+                        return newValue;
+                } else if (remove(key, oldValue)) {
+                    return null;
+                }
+                oldValue = get(key);
+            } else {
+                if ((oldValue = putIfAbsent(key, value)) == null) {
+                    return value;
+                }
+            }
+        }
+    }
+
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implNote This implementation assumes that the ConcurrentMap cannot
+     * contain null values and get() returning null unambiguously means the key
+     * is absent. Implementations which support null values
+     * <strong>must</strong> override this default implementation.
+     */
+    @Override
     default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
         Objects.requireNonNull(function);
         forEach((k,v) -> {