blockingqueue.java

来自「java pos,你可以直接编译运行,」· Java 代码 · 共 139 行

/*
 * Copyright (c) 2000 jPOS.org.  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 jPOS project 
 *    (http://www.jpos.org/)". Alternately, this acknowledgment may 
 *    appear in the software itself, if and wherever such third-party 
 *    acknowledgments normally appear.
 *
 * 4. The names "jPOS" and "jPOS.org" must not be used to endorse 
 *    or promote products derived from this software without prior 
 *    written permission. For written permission, please contact 
 *    [e-mail].
 *
 * 5. Products derived from this software may not be called "jPOS",
 *    nor may "jPOS" appear in their name, without prior written
 *    permission of the jPOS project.
 *
 * 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 THE JPOS PROJECT 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 the jPOS Project.  For more
 * information please see <http://www.jpos.org/>.
 */

package org.jpos.util;

import java.util.LinkedList;

/**
 * implements a blocking queue 
 * @see ThreadPool
 * @since 1.1
 */
public class BlockingQueue {
    private LinkedList queue = new LinkedList();
    private boolean closed = false;
    private int consumers = 0;

    public static class Closed extends RuntimeException {
        public Closed() {
            super ("queue closed");
        }
    }

    public synchronized void enqueue (Object o) throws Closed {
        if (closed)
            throw new Closed();
        queue.addLast (o);
        notify();
    }
    public synchronized void requeue (Object o) throws Closed {
        if (closed)
            throw new Closed();
        queue.addFirst (o);
        notify();
    }

    public synchronized Object dequeue()
        throws InterruptedException, Closed
    {
        consumers++;
        try {
            while (queue.size() == 0) {
                wait();
                if (closed)
                    throw new Closed();
            }
        } finally {
            consumers--;
        }
        return queue.removeFirst();
    }

    public synchronized Object dequeue (long timeout)
        throws InterruptedException, Closed
    {
        if (timeout == 0)
            return dequeue ();

        consumers++;
        long maxTime = System.currentTimeMillis() + timeout;
        try {
            while (queue.size() == 0 && System.currentTimeMillis() < maxTime) {
                wait (timeout);
                if (closed)
                    throw new Closed();
            }
        } finally {
            consumers--;
        }
        return queue.size() > 0 ? queue.removeFirst() : null;
    }
    public synchronized void close() {
        closed = true;
        notifyAll();
    }
    public synchronized int consumerCount() {
        return consumers;
    }
    public synchronized boolean ready() {
        return !closed;
    }
    public synchronized int pending() {
        return queue.size();
    }
    public LinkedList getQueue () {
        return queue;
    }
    public void setQueue (LinkedList queue) {
        this.queue = queue;
    }
}