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src/java.base/share/classes/java/util/Enumeration.java
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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();
+ }
+ };
+ }
}
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