生产者消费者

生产者消费者

public class ProducerConsumerDemo {
    public static void main(String[] args) {
        Resource r = new Resource();

        Producer pro = new Producer(r);
        Consumer con = new Consumer(r);

        Thread t1 = new Thread(pro);
        Thread t2 = new Thread(pro);
        Thread t3 = new Thread(con);
        Thread t4 = new Thread(con);

        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
}

/*
 * 对于多个生产者和消费者。 为什么要定义while判断标记。 原因：让被唤醒的线程再一次判断标记。 为什么定义notifyAll， 因为需要唤醒对方线程。
 * 因为只用notify，容易出现只唤醒本方线程的情况。导致程序中的所有线程都等待。
 */
class Resource {
    private String name;
    private int count = 1;
    private boolean flag = false;

    /*
     * 生产商品
     */
    public synchronized void set(String name) {
        while (flag)
            try {
                this.wait();
            } catch (Exception e) {
            }
        this.name = name + "--" + count++;

        System.out.println(Thread.currentThread().getName() + "...生产者.."
                + this.name);
        flag = true;
        this.notifyAll();
    }

    /*
     * 消费商品
     */
    public synchronized void out() {
        while (!flag)
            try {
                wait();
            } catch (Exception e) {
            }
        System.out.println(Thread.currentThread().getName() + "...消费者........."
                + this.name);
        flag = false;
        this.notifyAll();
    }
}

class Producer implements Runnable {
    private Resource res;

    Producer(Resource res) {
        this.res = res;
    }

    public void run() {
        while (true) {
            res.set("+商品+");
        }
    }
}

class Consumer implements Runnable {
    private Resource res;

    Consumer(Resource res) {
        this.res = res;
    }

    public void run() {
        while (true) {
            res.out();
        }
    }
}

JDK1.5 中提供了多线程升级解决方案。 将同步Synchronized替换成现实Lock操作。
将Object中的wait，notify notifyAll，替换了Condition对象。 该对象可以Lock锁 进行获取。 该示例中，实现了本方只唤醒对方操作。
Lock:替代了Synchronized lock unlock newCondition()
Condition：替代了Object wait notify notifyAll await(); signal(); signalAll();

import java.util.concurrent.locks.*;

public class ProducerConsumerDemo2 {
    public static void main(String[] args) {
        Resource r = new Resource();

        Producer pro = new Producer(r);
        Consumer con = new Consumer(r);

        Thread t1 = new Thread(pro);
        Thread t2 = new Thread(pro);
        Thread t3 = new Thread(con);
        Thread t4 = new Thread(con);

        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
}

class Resource {
    private String name;
    private int count = 1;
    private boolean flag = false;

    private Lock lock = new ReentrantLock();

    private Condition condition_pro = lock.newCondition();
    private Condition condition_con = lock.newCondition();

    public void set(String name) throws InterruptedException {
        lock.lock();
        try {
            while (flag)
                condition_pro.await();// t1,t2
            this.name = name + "--" + count++;

            System.out.println(Thread.currentThread().getName() + "...生产者.."
                    + this.name);
            flag = true;
            condition_con.signal();
        } finally {
            lock.unlock();// 释放锁的动作一定要执行。
        }
    }

    // t3 t4
    public void out() throws InterruptedException {
        lock.lock();
        try {
            while (!flag)
                condition_con.await();
            System.out.println(Thread.currentThread().getName()
                    + "...消费者........." + this.name);
            flag = false;
            condition_pro.signal();
        } finally {
            lock.unlock();
        }

    }
}

class Producer implements Runnable {
    private Resource res;

    Producer(Resource res) {
        this.res = res;
    }

    public void run() {
        while (true) {
            try {
                res.set("+商品+");
            } catch (InterruptedException e) {
            }

        }
    }
}

class Consumer implements Runnable {
    private Resource res;

    Consumer(Resource res) {
        this.res = res;
    }

    public void run() {
        while (true) {
            try {
                res.out();
            } catch (InterruptedException e) {
            }
        }
    }
}

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