src/share/classes/java/util/concurrent/ConcurrentMap.java

rev 6858 : 8004518: Add in-place operations to Map
8010122: Add defaults for ConcurrentMap operations to Map
Reviewed-by: darcy, briangoetz, mduigou, dholmes, ulfzibis
Contributed-by: Doug Lea <dl at cs.oswego.edu>, Henry Jen <henry.jen@oracle.com>, Akhil Arora <akhil.arora@oracle.com>, Peter Levart <peter.levart@gmail.com>

*** 55,64 ****
--- 55,79 ----
   * @author Doug Lea
   * @param <K> the type of keys maintained by this map
   * @param <V> the type of mapped values
   */
  public interface ConcurrentMap<K, V> extends Map<K, V> {
+ 
+     /**
+      * {@inheritDoc}
+      *
+      * @implNote This implementation assumes that the ConcurrentMap cannot
+      * contain null values and get() returning null unambiguously means no
+      * mapping is present. Implementations which support null values must
+      * override this default implementation.
+      */
+     @Override
+     default V getOrDefault(Object key, V defaultValue) {
+         V v;
+         return (null != (v = get(key))) ? v : defaultValue;
+     }
+ 
      /**
       * If the specified key is not already associated
       * with a value, associate it with the given value.
       * This is equivalent to
       *  <pre> {@code