01: /*
02: * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
03: *
04: * This file is part of Resin(R) Open Source
05: *
06: * Each copy or derived work must preserve the copyright notice and this
07: * notice unmodified.
08: *
09: * 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;
32:
33: /**
34: * A null iterator
35: */
36: public class NullIterator<E> implements ListIterator<E> {
37: private static NullIterator _singleton;
38:
39: public static NullIterator create() {
40: if (_singleton == null)
41: _singleton = new NullIterator();
42:
43: return _singleton;
44: }
45:
46: public boolean hasNext() {
47: return false;
48: }
49:
50: public E next() {
51: return null;
52: }
53:
54: public int nextIndex() {
55: return -1;
56: }
57:
58: public boolean hasPrevious() {
59: return false;
60: }
61:
62: public E previous() {
63: return null;
64: }
65:
66: public int previousIndex() {
67: return -1;
68: }
69:
70: public void add(E o) {
71: throw new UnsupportedOperationException();
72: }
73:
74: public void set(E o) {
75: throw new UnsupportedOperationException();
76: }
77:
78: public void remove() {
79: throw new UnsupportedOperationException();
80: }
81: }
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