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Java > Open Source Codes > net > sf > jga > util > EmptyIterator


1 // ============================================================================
2 // $Id: EmptyIterator.java,v 1.6 2005/08/02 23:45:22 davidahall Exp $
3 // Copyright (c) 2003-2005 David A. Hall
4 // ============================================================================
5 // The contents of this file are subject to the Common Development and
6 // Distribution License (CDDL), Version 1.0 (the License); you may not use this
7 // file except in compliance with the License. You should have received a copy
8 // of the the License along with this file: if not, a copy of the License is
9 // available from Sun Microsystems, Inc.
10 //
11 // http://www.sun.com/cddl/cddl.html
12 //
13 // From time to time, the license steward (initially Sun Microsystems, Inc.) may
14 // publish revised and/or new versions of the License. You may not use,
15 // distribute, or otherwise make this file available under subsequent versions
16 // of the License.
17 //
18 // Alternatively, the contents of this file may be used under the terms of the
19 // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
20 // case the provisions of the LGPL are applicable instead of those above. If you
21 // wish to allow use of your version of this file only under the terms of the
22 // LGPL, and not to allow others to use your version of this file under the
23 // terms of the CDDL, indicate your decision by deleting the provisions above
24 // and replace them with the notice and other provisions required by the LGPL.
25 // If you do not delete the provisions above, a recipient may use your version
26 // of this file under the terms of either the CDDL or the LGPL.
27 //
28 // This library is distributed in the hope that it will be useful,
29 // but WITHOUT ANY WARRANTY; without even the implied warranty of
30 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
31 // ============================================================================
32 package net.sf.jga.util;
33
34 import java.util.ListIterator JavaDoc;
35 import java.util.NoSuchElementException JavaDoc;
36 import java.util.Iterator JavaDoc;
37
38 /**
39  * Iterator over an empty set of elements.
40  *
41  * @author <a HREF="mailto:davidahall@users.sf.net">David A. Hall</a>
42  */
43
44 public class EmptyIterator<T> implements ListIterator JavaDoc<T>, Iterable JavaDoc<T> {
45     
46     // - - - - - - - - - - -
47 // Iterable<T> interface
48 // - - - - - - - - - - -
49
50     public Iterator JavaDoc<T> iterator() { return this; }
51     
52     // - - - - - - - - - - - - -
53 // ListIterator<T> interface
54 // - - - - - - - - - - - - -
55
56     /**
57      * Returns false: the set of elements is empty by definition
58      * @return false
59      */
60     public boolean hasNext() { return false; }
61
62     /**
63      * throws NoSuchElement exception
64      *
65      * @return nothing
66      */
67     public T next() { throw new NoSuchElementException JavaDoc(); }
68
69     /**
70      * Returns false: the set of elements is empty by definition
71      * @return false
72      */
73     public boolean hasPrevious() { return false; }
74
75     /**
76      * throws NoSuchElement exception
77      *
78      * @return nothing
79      */
80     public T previous() { throw new NoSuchElementException JavaDoc(); }
81
82     /**
83      * returns the size of the list (0, in this case)
84      *
85      * @return 0
86      */
87     public int nextIndex() { return 0; }
88
89     /**
90      * returns -1, as there is no previous
91      *
92      * @return -1;
93      */
94     public int previousIndex() { return -1; }
95     
96     /**
97      * throws UnsupportedOperationException
98      */
99     public void remove() { throw new UnsupportedOperationException JavaDoc(); }
100
101     /**
102      * throws UnsupportedOperationException
103      */
104     public void set (T arg) { throw new UnsupportedOperationException JavaDoc(); }
105
106     /**
107      * throws UnsupportedOperationException
108      */
109     public void add (T arg) { throw new UnsupportedOperationException JavaDoc(); }
110
111 }
112
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