    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}