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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
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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   JDK1.0
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  }