ProdCons2.java Source code

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Here is the source code for ProdCons2.java

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/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS 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 AUTHOR OR 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.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */

import java.util.*;
import java.io.*;

/** Producer-consumer in Java, Take II.
 */
public class ProdCons2 {

    /** Throughout the code, this is the object we synchronize on so this
     * is also the object we wait() and notifyAll() on.
     */
    protected LinkedList list = new LinkedList();
    protected int MAX = 10;
    protected boolean done = false; // Also protected by lock on list.

    /** Inner class representing the Producer side */
    class Producer extends Thread {

        public void run() {
            while (true) {
                Object justProduced = getRequestFromNetwork();
                // Get request from the network - outside the synch section.
                // We're simulating this actually reading from a client, and it
                // might have to wait for hours if the client is having coffee.
                synchronized (list) {
                    while (list.size() == MAX) // queue "full"
                        try {
                            System.out.println("Producer WAITING");
                            list.wait(); // Limit the size
                        } catch (InterruptedException ex) {
                            System.out.println("Producer INTERRUPTED");
                        }
                    list.addFirst(justProduced);
                    list.notifyAll(); // must own the lock
                    System.out.println("Produced 1; List size now " + list.size());
                    if (done)
                        break;
                    // yield();   // Useful for green threads & demo programs.
                }
            }
        }

        Object getRequestFromNetwork() { // Simulation of reading from client
            // try {
            //    Thread.sleep(10); // simulate time passing during read
            // } catch (InterruptedException ex) {
            //    System.out.println("Producer Read INTERRUPTED");
            // }
            return (new Object());
        }
    }

    /** Inner class representing the Consumer side */
    class Consumer extends Thread {
        public void run() {
            while (true) {
                Object obj = null;
                synchronized (list) {
                    while (list.size() == 0) {
                        try {
                            System.out.println("CONSUMER WAITING");
                            list.wait(); // must own the lock
                        } catch (InterruptedException ex) {
                            System.out.println("CONSUMER INTERRUPTED");
                        }
                    }
                    obj = list.removeLast();
                    list.notifyAll();
                    int len = list.size();
                    System.out.println("List size now " + len);
                    if (done)
                        break;
                }
                process(obj); // Outside synch section (could take time)
                //yield(); DITTO
            }
        }

        void process(Object obj) {
            // Thread.sleep(xxx) // Simulate time passing
            System.out.println("Consuming object " + obj);
        }
    }

    ProdCons2(int nP, int nC) {
        for (int i = 0; i < nP; i++)
            new Producer().start();
        for (int i = 0; i < nC; i++)
            new Consumer().start();
    }

    public static void main(String[] args) throws IOException, InterruptedException {

        // Start producers and consumers
        int numProducers = 4;
        int numConsumers = 3;
        ProdCons2 pc = new ProdCons2(numProducers, numConsumers);

        // Let it run for, say, 10 seconds
        Thread.sleep(10 * 1000);

        // End of simulation - shut down gracefully
        synchronized (pc.list) {
            pc.done = true;
            pc.list.notifyAll();
        }
    }
}