001 /* ========================================================================
002 * JCommon : a free general purpose class library for the Java(tm) platform
003 * ========================================================================
004 *
005 * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
006 *
007 * Project Info: http://www.jfree.org/jcommon/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it
010 * under the terms of the GNU Lesser General Public License as published by
011 * the Free Software Foundation; either version 2.1 of the License, or
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
022 * USA.
023 *
024 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
025 * in the United States and other countries.]
026 *
027 * ---------------------
028 * ReadOnlyIterator.java
029 * ---------------------
030 * (C)opyright 2003, 2004, by Thomas Morgner and Contributors.
031 *
032 * Original Author: Thomas Morgner;
033 * Contributor(s): -;
034 *
035 * $Id: ReadOnlyIterator.java,v 1.2 2005/10/18 13:24:19 mungady Exp $
036 *
037 * Changes
038 * -------------------------
039 * 18-Jul-2003 : Initial version
040 *
041 */
042
043 package org.jfree.util;
044
045 import java.util.Iterator;
046
047 /**
048 * Protects an given iterator by preventing calls to remove().
049 *
050 * @author Thomas Morgner
051 */
052 public class ReadOnlyIterator implements Iterator {
053
054 /** The base iterator which we protect. */
055 private Iterator base;
056
057 /**
058 * Creates a new read-only iterator for the given iterator.
059 *
060 * @param it the iterator.
061 */
062 public ReadOnlyIterator(final Iterator it) {
063 if (it == null) {
064 throw new NullPointerException("Base iterator is null.");
065 }
066 this.base = it;
067 }
068
069 /**
070 * Returns <tt>true</tt> if the iteration has more elements. (In other
071 * words, returns <tt>true</tt> if <tt>next</tt> would return an element
072 * rather than throwing an exception.)
073 *
074 * @return <tt>true</tt> if the iterator has more elements.
075 */
076 public boolean hasNext() {
077 return this.base.hasNext();
078 }
079
080 /**
081 * Returns the next element in the iteration.
082 * Throws NoSuchElementException when iteration has no more elements.
083 *
084 * @return the next element in the iteration.
085 */
086 public Object next() {
087 return this.base.next();
088 }
089
090 /**
091 * Throws <code>UnsupportedOperationException</code>.
092 */
093 public void remove() {
094 throw new UnsupportedOperationException();
095 }
096 }