生产者消费者.md

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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