peerviewrandomwithreplacestrategy.java

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

/*
 * 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.
 *
 * $Id: PeerViewRandomWithReplaceStrategy.java,v 1.6 2004/05/18 19:22:11 bondolo Exp $
 */
package net.jxta.impl.rendezvous.rpv;


import java.util.Random;
import java.util.SortedSet;
import java.util.Iterator;


/**
 * Random with replacement
 **/
class PeerViewRandomWithReplaceStrategy implements PeerViewStrategy {
    
    private static Random random = new Random();
    private SortedSet set = null;
    
    PeerViewRandomWithReplaceStrategy(SortedSet set) {
        this.set = set;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void reset() {}
    
    /**
     *  {@inheritDoc}
     **/
    public PeerViewElement next() {
        synchronized (set) {
            if (set.isEmpty()) {
                return null;
            }
            
            int i = random.nextInt(set.size());
            
            // return the ith element
            int n = 0;
            Iterator si = set.iterator();
            
            while (n < i) {
                si.next();
                n++;
            }

            return (PeerViewElement) si.next();
        }
    }
}