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Java > Open Source Codes > com > caucho > util > NullIterator


1 /*
2  * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3  *
4  * This file is part of Resin(R) Open Source
5  *
6  * Each copy or derived work must preserve the copyright notice and this
7  * notice unmodified.
8  *
9  * Resin Open Source is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * Resin Open Source is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17  * of NON-INFRINGEMENT. See the GNU General Public License for more
18  * details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with Resin Open Source; if not, write to the
22  * Free SoftwareFoundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.util;
30
31 import java.util.ListIterator JavaDoc;
32
33 /**
34  * A null iterator
35  */
36 public class NullIterator<E> implements ListIterator JavaDoc<E> {
37   private static NullIterator _singleton;
38
39   public static NullIterator create()
40   {
41     if (_singleton == null)
42       _singleton = new NullIterator();
43
44     return _singleton;
45   }
46
47   public boolean hasNext()
48   {
49     return false;
50   }
51
52   public E next()
53   {
54     return null;
55   }
56
57   public int nextIndex()
58   {
59     return -1;
60   }
61
62   public boolean hasPrevious()
63   {
64     return false;
65   }
66
67   public E previous()
68   {
69     return null;
70   }
71
72   public int previousIndex()
73   {
74     return -1;
75   }
76
77   public void add(E o)
78   {
79     throw new UnsupportedOperationException JavaDoc();
80   }
81
82   public void set(E o)
83   {
84     throw new UnsupportedOperationException JavaDoc();
85   }
86
87   public void remove()
88   {
89     throw new UnsupportedOperationException JavaDoc();
90   }
91 }
92
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