001: // ============================================================================
002: // $Id: EmptyIterator.java,v 1.6 2005/08/02 23:45:22 davidahall Exp $
003: // Copyright (c) 2003-2005 David A. Hall
004: // ============================================================================
005: // The contents of this file are subject to the Common Development and
006: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
007: // file except in compliance with the License. You should have received a copy
008: // of the the License along with this file: if not, a copy of the License is
009: // available from Sun Microsystems, Inc.
010: //
011: // http://www.sun.com/cddl/cddl.html
012: //
013: // From time to time, the license steward (initially Sun Microsystems, Inc.) may
014: // publish revised and/or new versions of the License. You may not use,
015: // distribute, or otherwise make this file available under subsequent versions
016: // of the License.
017: //
018: // Alternatively, the contents of this file may be used under the terms of the
019: // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
020: // case the provisions of the LGPL are applicable instead of those above. If you
021: // wish to allow use of your version of this file only under the terms of the
022: // LGPL, and not to allow others to use your version of this file under the
023: // terms of the CDDL, indicate your decision by deleting the provisions above
024: // and replace them with the notice and other provisions required by the LGPL.
025: // If you do not delete the provisions above, a recipient may use your version
026: // of this file under the terms of either the CDDL or the LGPL.
027: //
028: // This library is distributed in the hope that it will be useful,
029: // but WITHOUT ANY WARRANTY; without even the implied warranty of
030: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
031: // ============================================================================
032: package net.sf.jga.util;
033:
034: import java.util.ListIterator;
035: import java.util.NoSuchElementException;
036: import java.util.Iterator;
037:
038: /**
039: * Iterator over an empty set of elements.
040: *
041: * @author <a href="mailto:davidahall@users.sf.net">David A. Hall</a>
042: */
043:
044: public class EmptyIterator<T> implements ListIterator<T>, Iterable<T> {
045:
046: // - - - - - - - - - - -
047: // Iterable<T> interface
048: // - - - - - - - - - - -
049:
050: public Iterator<T> iterator() {
051: return this ;
052: }
053:
054: // - - - - - - - - - - - - -
055: // ListIterator<T> interface
056: // - - - - - - - - - - - - -
057:
058: /**
059: * Returns false: the set of elements is empty by definition
060: * @return false
061: */
062: public boolean hasNext() {
063: return false;
064: }
065:
066: /**
067: * throws NoSuchElement exception
068: *
069: * @return nothing
070: */
071: public T next() {
072: throw new NoSuchElementException();
073: }
074:
075: /**
076: * Returns false: the set of elements is empty by definition
077: * @return false
078: */
079: public boolean hasPrevious() {
080: return false;
081: }
082:
083: /**
084: * throws NoSuchElement exception
085: *
086: * @return nothing
087: */
088: public T previous() {
089: throw new NoSuchElementException();
090: }
091:
092: /**
093: * returns the size of the list (0, in this case)
094: *
095: * @return 0
096: */
097: public int nextIndex() {
098: return 0;
099: }
100:
101: /**
102: * returns -1, as there is no previous
103: *
104: * @return -1;
105: */
106: public int previousIndex() {
107: return -1;
108: }
109:
110: /**
111: * throws UnsupportedOperationException
112: */
113: public void remove() {
114: throw new UnsupportedOperationException();
115: }
116:
117: /**
118: * throws UnsupportedOperationException
119: */
120: public void set(T arg) {
121: throw new UnsupportedOperationException();
122: }
123:
124: /**
125: * throws UnsupportedOperationException
126: */
127: public void add(T arg) {
128: throw new UnsupportedOperationException();
129: }
130:
131: }
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