src/share/classes/java/lang/AutoCloseable.java

*** 39,47 ****
--- 39,54 ----
       *
       * <p>Classes implementing this method are strongly encouraged to
       * be declared to throw more specific exceptions (or no exception
       * at all, if the close cannot fail).
       *
+      * <p>Note that unlike the {@link java.io.Closeable#close close}
+      * method of {@link java.io.Closeable}, this {@code close} method
+      * is <em>not</em> required to be idempotent.  In other words,
+      * calling this {@code close} method more than once may have some
+      * visible side effect, unlike {@code Closeable.close} which is
+      * required to have no effect if called more than once.
+      *
       * @throws Exception if this resource cannot be closed
       */
      void close() throws Exception;
  }