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JCommon is a free general purpose Java class library that is used in several projects at www.jfree.org, including JFreeChart and JFreeReport.

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/* ========================================================================
 * JCommon : a free general purpose class library for the Java(tm) platform
 * ========================================================================
 *
 * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
 * 
 * Project Info:  http://www.jfree.org/jcommon/index.html
 *
 * This library is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by 
 * the Free Software Foundation; either version 2.1 of the License, or 
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
 * USA.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 * 
 * ---------------------
 * ReadOnlyIterator.java
 * ---------------------
 * (C)opyright 2003, 2004, by Thomas Morgner and Contributors.
 *
 * Original Author:  Thomas Morgner;
 * Contributor(s):   -;
 *
 * $Id: ReadOnlyIterator.java,v 1.2 2005/10/18 13:24:19 mungady Exp $
 *
 * Changes
 * -------------------------
 * 18-Jul-2003 : Initial version
 *
 */

package org.jfree.util;

import java.util.Iterator;

/**
 * Protects an given iterator by preventing calls to remove().
 *
 * @author Thomas Morgner
 */
public class ReadOnlyIterator implements Iterator {

    /** The base iterator which we protect. */
    private Iterator base;

    /**
     * Creates a new read-only iterator for the given iterator.
     *
     * @param it the iterator.
     */
    public ReadOnlyIterator(final Iterator it) {
        if (it == null) {
            throw new NullPointerException("Base iterator is null.");
        }
        this.base = it;
    }

    /**
     * Returns true if the iteration has more elements. (In other
     * words, returns true if next would return an element
     * rather than throwing an exception.)
     *
     * @return true if the iterator has more elements.
     */
    public boolean hasNext() {
        return this.base.hasNext();
    }

    /**
     * Returns the next element in the iteration.
     * Throws NoSuchElementException when iteration has no more elements.
     * 
     * @return the next element in the iteration.
     */
    public Object next() {
        return this.base.next();
    }

    /**
     * Throws UnsupportedOperationException.
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }
}