src/java.base/share/classes/java/util/Enumeration.java

rev 11962 : 8072726: add adapter to convert Enumeration to Iterator
Reviewed-by: XXX

*** 1,7 ****
  /*
!  * Copyright (c) 1994, 2005, 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.  Oracle designates this
--- 1,7 ----
  /*
!  * Copyright (c) 1994, 2015, 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.  Oracle designates this
*** 74,79 ****
--- 74,134 ----
       *
       * @return     the next element of this enumeration.
       * @exception  NoSuchElementException  if no more elements exist.
       */
      E nextElement();
+ 
+     /**
+      * Returns an {@link Iterator} whose elements are the same as the
+      * elements of this {@code Enumeration}. The results are undefined
+      * if this method is called more than once, or if this Enumeration's
+      * other methods are called after {@code asIterator} has been called.
+      *
+      * @apiNote
+      * This method is intended to help adapt code that produces
+      * {@code Enumeration} instances to code that consumes {@code Iterator}
+      * or {@code Iterable} instances. For example, the
+      * {@link java.security.PermissionCollection PermissionCollection.elements()}
+      * method returns an {@code Enumeration<Permission>}. This can be adapted
+      * for use in an enhanced-for loop as follows:
+      *
+      * <pre>{@code
+      *     PermissionCollection pc = ... ;
+      *     Iterable<Permission> permsIterable = () -> pc.elements().asIterator();
+      *     for (Permission p : permsIterable) {
+      *         doSomethingWithPermission(p);
+      *     }
+      * }</pre>
+      *
+      * A {@code Stream<Permission>} could be created from an
+      * {@code Enumeration<Permission>} as follows:
+      *
+      * <pre>{@code
+      *     Stream<Permission> permsStream = StreamSupport.stream(
+      *         Spliterators.spliteratorUnknownSize(
+      *             pc.elements().asIterator(),
+      *             Spliterator.ORDERED | Spliterator.IMMUTABLE),
+      *         false);
+      * }</pre>
+      *
+      * @implSpec
+      * The returned Iterator's {@link Iterator#hasNext hasNext} method calls and returns
+      * the value from this Enumeration's {@code hasMoreElements} method; its
+      * {@link Iterator#next next} method calls and returns the value from this Enumeration's
+      * {@code nextElement} method; and its {@link Iterator#remove remove} method throws
+      * {@code UnsupportedOperationException}.
+      *
+      * @return an Iterator derived from this Enumeration
+      *
+      * @since 1.9
+      */
+     default Iterator<E> asIterator() {
+         return new Iterator<E>() {
+             @Override public boolean hasNext() {
+                 return Enumeration.this.hasMoreElements();
+             }
+             @Override public E next() {
+                 return Enumeration.this.nextElement();
+             }
+         };
+     }
  }