sequenceiterator.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/*
 *
 * $Id: SequenceIterator.java,v 1.3 2003/06/05 17:11:06 bondolo Exp $
 *
 * Copyright (c) 2002 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more information on
 * Project JXTA, please see <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *
 */

package net.jxta.impl.util;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import java.util.NoSuchElementException;

/**
 *  This class lets you combine a number of iterators.
 */
public class SequenceIterator implements Iterator {
    
    private Iterator iterators;
    
    private Iterator current = null;
    
    private Iterator previous = null;
    
    /**
     * Creates a new instance of SequenceIterator
     *
     * @param iterators An iterator containing instances of Iterator. This
     * iterator will iterate over all of the item in these iterators.
     **/
    public SequenceIterator( Iterator iterators ) {
        this.iterators = iterators;
    }
    
    /**
     * Creates a new instance of SequenceIterator
     **/
    public SequenceIterator( Iterator first, Iterator second ) {
        List iterators = new ArrayList(2);
        
        iterators.add( first );
        iterators.add( second );
        
        this.iterators = iterators.iterator();
    }
    
    /**
     *  {@inheritDoc}
     **/
    public boolean hasNext() {
        
        if( (null == current) || (!current.hasNext()) ) {
            do {
                if( !iterators.hasNext() )
                    return false;
                
                current = (Iterator) iterators.next();
            } while( !current.hasNext() );
        }
        
        return true;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public Object next() {
        if( !hasNext() )
            throw new NoSuchElementException( "no next element" );

        previous = current;
        return current.next();
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void remove() {
        if( null == previous )
            throw new IllegalStateException( "next() has not been called" );
        
        previous.remove();
        previous = null;
    }
}