1 /*
   2  * Copyright (c) 1994, 2005, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.util;
  27 
  28 /**
  29  * An object that implements the Enumeration interface generates a
  30  * series of elements, one at a time. Successive calls to the
  31  * <code>nextElement</code> method return successive elements of the
  32  * series.
  33  * <p>
  34  * For example, to print all elements of a <tt>Vector&lt;E&gt;</tt> <i>v</i>:
  35  * <pre>
  36  *   for (Enumeration&lt;E&gt; e = v.elements(); e.hasMoreElements();)
  37  *       System.out.println(e.nextElement());</pre>
  38  * <p>
  39  * Methods are provided to enumerate through the elements of a
  40  * vector, the keys of a hashtable, and the values in a hashtable.
  41  * Enumerations are also used to specify the input streams to a
  42  * <code>SequenceInputStream</code>.
  43  * <p>
  44  * NOTE: The functionality of this interface is duplicated by the Iterator
  45  * interface.  In addition, Iterator adds an optional remove operation, and
  46  * has shorter method names.  New implementations should consider using
  47  * Iterator in preference to Enumeration.
  48  *
  49  * @see     java.util.Iterator
  50  * @see     java.io.SequenceInputStream
  51  * @see     java.util.Enumeration#nextElement()
  52  * @see     java.util.Hashtable
  53  * @see     java.util.Hashtable#elements()
  54  * @see     java.util.Hashtable#keys()
  55  * @see     java.util.Vector
  56  * @see     java.util.Vector#elements()
  57  *
  58  * @author  Lee Boynton
  59  * @since   1.0
  60  */
  61 public interface Enumeration<E> {
  62     /**
  63      * Tests if this enumeration contains more elements.
  64      *
  65      * @return  <code>true</code> if and only if this enumeration object
  66      *           contains at least one more element to provide;
  67      *          <code>false</code> otherwise.
  68      */
  69     boolean hasMoreElements();
  70 
  71     /**
  72      * Returns the next element of this enumeration if this enumeration
  73      * object has at least one more element to provide.
  74      *
  75      * @return     the next element of this enumeration.
  76      * @exception  NoSuchElementException  if no more elements exist.
  77      */
  78     E nextElement();
  79 }
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