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
043package org.jfree.util;
044
045import java.util.Iterator;
046
047/**
048 * Protects an given iterator by preventing calls to remove().
049 *
050 * @author Thomas Morgner
051 */
052public 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}