src/share/classes/java/util/prefs/AbstractPreferences.java

*** 303,314 ****
--- 303,316 ----
       * event dispatch thread.
       *
       * @param key key whose mapping is to be removed from the preference node.
       * @throws IllegalStateException if this node (or an ancestor) has been
       *         removed with the {@link #removeNode()} method.
+      * @throws NullPointerException {@inheritDoc}.
       */
      public void remove(String key) {
+         Objects.requireNonNull(key, "Specified key cannot be null");
          synchronized(lock) {
              if (removed)
                  throw new IllegalStateException("Node has been removed.");
  
              removeSpi(key);