1 /*
2 * Copyright (c) 2003-2008 by Cosylab d. d.
3 *
4 * This file is part of Java-Common.
5 *
6 * Java-Common is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
10 *
11 * Java-Common is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with Java-Common. If not, see <http://www.gnu.org/licenses/>.
18 */
19
20 package com.cosylab.util;
21
22 import java.util.Enumeration;
23
24
25 /**
26 * This class defines enumeration with no elements. Its intended use is as
27 * return value when method returns enumeration that has no elements. This is
28 * a singleton implementation and instance of this class is obtained using
29 * <code>EmptyEnumeration.getInstance()</code> method.
30 *
31 * <p>
32 * This class should serve as a convenience implementation of an interface.
33 * </p>
34 *
35 * @author <a href="mailto:ales.pucelj@cosylab.com">Ales Pucelj</a>
36 * @version $id$
37 */
38 public final class EmptyEnumeration implements Enumeration
39 {
40 private static final Enumeration INSTANCE = new EmptyEnumeration();
41
42 /**
43 * Private singleton constructor.
44 */
45 private EmptyEnumeration()
46 {
47 super();
48 }
49
50 /**
51 * Returns singleton instance of this class.
52 *
53 * @return Instance of Enumeration.
54 */
55 public static final Enumeration getInstance()
56 {
57 return INSTANCE;
58 }
59
60 /**
61 * Returns false.
62 *
63 * @see java.util.Enumeration#hasMoreElements()
64 */
65 public boolean hasMoreElements()
66 {
67 return false;
68 }
69
70 /**
71 * Returns null.
72 *
73 * @see java.util.Enumeration#nextElement()
74 */
75 public Object nextElement()
76 {
77 return null;
78 }
79 }
80
81 /* __oOo__ */