Java生产者与消费者（上）

本文来自http://blog.csdn.net/liuxian13183/ ，引用必须注明出处！

生产与消费者模式，是编程中最常用的模式之一，在多线程中应用比较明显。个人理解：在自助餐厅，厨师在不断做菜放桌子上，吃货不断从桌子上拿东西，这中间如果桌子上已经摆满那厨师要暂停工作 ，桌子上已没有食物则吃货要暂停拿东西吃。

先决条件，食材充足，桌子一定。

本程序设计原则：由于synchronized加锁方法，使得内部的所有变量也被加锁；我们采取多线程操作，故中间要用sleep（为了把锁让给别人，比如A上厕所开启sleep模式，B就偷偷拿上锁溜进来，方便后再还锁给A，要保证B修改同一个资源的话，要在A sleep的时间内完成），以便其他线程可以使用（windows多线程亦采取同样设计原则），sleep很短的时间，故用户不会有停滞感。为结果清晰，producer和consumer共执行操作50次，则程序停止运行。

桌子：

count，即桌子数量一定，produce和consume均对count操作。当蛋糕数大于等于桌子数时，生产线程要等待；当蛋糕数少于或等于0时，消费线程要等待。notifyAll是唤醒所有线程，如果生产线程watit时，消费线程已经把cake吃光，则要唤醒生产线程，反之亦然，故用notifyAll，而notify仅唤醒当前线程，在这里是没有用的。

public class Table {

	private volatile int count;
	private int cake;
	private int stopCounts;

	public Table(int count) {
		// TODO Auto-generated constructor stub
		this.count = count;
	}

	public synchronized void produce(String threadName) throws InterruptedException {
		while (cake >= count) {
			System.out.println(threadName + " begin to wait !");
			wait();
			System.out.println(threadName + " stop waiting !");
		}
		System.out.println(threadName + " produce:" + ++cake);
		notifyAll();
		if (++stopCounts > 50) {
			System.out.println(threadName + " stop at last !");
			System.exit(0);
		}
	}

	public synchronized void consume(String threadName) throws InterruptedException {
		while (cake <= 0) {
			System.out.println(threadName + " begin to wait !");
			wait();
			System.out.println(threadName + " stop waiting !");

		}
		System.out.println(threadName + " consume:" + cake--);
		notifyAll();

		if (++stopCounts > 50) {
			System.out.println(threadName + " stop at last !");
			System.exit(0);
		}
	}
}

生产者：

生产蛋糕，一次停止1毫秒

public class Producer extends Thread {
	Table table;
	String threadName;

	public Producer(String string, Table table) {
		// TODO Auto-generated constructor stub
		this.table = table;
		this.threadName=string;
		this.setName(threadName);
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		super.run();
		try {
			while (true) {
				table.produce(threadName);
				sleep(1);
			}
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

消费者：

消费蛋糕，一次停止1毫秒

public class Consumer extends Thread {
	Table table;
	String threadName;

	public Consumer(String string, Table table) {
		// TODO Auto-generated constructor stub
		this.table = table;
		this.threadName=string;
		this.setName(threadName);
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		super.run();
		try {
			while (true) {
				table.consume(threadName);
				sleep(1);
			}
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

验证程序：

多线程

public class TestCP {
	public static void main(String[] args) {
		Table table = new Table(5);
		Thread p1 = new Producer("Produce1",table);
		Thread c1 = new Consumer("Consumer1",table);
		Thread p2 = new Producer("Produce2",table);
		Thread c2 = new Consumer("Consumer2",table);
		p1.start();
		c1.start();
		p2.start();
		c2.start();
	}
}

验证结果：

Produce1 produce:1            //Producer1先生产一只cake
Produce2 produce:2           //Producer2得到锁生产一只
Consumer1 consume:2          //Consumer1先消费一只
Consumer2 consume:1          //Consumer2得到锁也消费一只
Consumer1 begin to wait !    //Consumer1得到锁开始等待
Produce1 produce:1           //Producer1开始生产
Produce2 produce:2           // Producer2开始生产
Consumer2 consume:2          //Consumer2开始消费
Consumer1 stop waiting !     //当cake数大于0，Consumer1停止等待
Consumer1 consume:1          //Consumer1开始消费
Consumer1 begin to wait !    //当cake数等于0，Consumer1开始等待
Consumer1 consume:1          //Consumer1开始消费
Consumer1 begin to wait !    //当cake数等于0，Consumer1开始等待
Produce2 produce:1           //..............................
Consumer1 stop waiting !
Consumer1 consume:1
Produce1 produce:1
Consumer2 consume:1
Consumer1 begin to wait !
Consumer2 begin to wait !
Produce1 produce:1
Produce2 produce:2
Consumer2 stop waiting !
Consumer2 consume:2
Consumer1 stop waiting !
Consumer1 consume:1
Consumer2 begin to wait !
Consumer1 begin to wait !
Produce1 produce:1
Consumer1 stop waiting !
Consumer1 consume:1
Consumer2 stop waiting !
Consumer2 begin to wait !
Produce2 produce:1
Consumer2 stop waiting !
Consumer2 consume:1
Consumer2 begin to wait !
Produce1 produce:1
Consumer1 consume:1
Consumer2 stop waiting !
Consumer2 begin to wait !
Produce2 produce:1
Consumer2 stop waiting !
Consumer2 consume:1
Produce1 produce:1
Produce2 produce:2
Consumer2 consume:2
Consumer1 consume:1
Consumer1 begin to wait !
Consumer2 begin to wait !
Produce1 produce:1
Produce2 produce:2
Consumer2 stop waiting !
Consumer2 consume:2
Consumer1 stop waiting !
Consumer1 consume:1
Consumer1 begin to wait !
Produce2 produce:1
Produce1 produce:2
Consumer1 stop waiting !
Consumer1 consume:2
Consumer2 consume:1
Consumer1 begin to wait !
Produce1 produce:1
Consumer2 consume:1
Produce2 produce:1
Consumer1 stop waiting !
Consumer1 consume:1
Consumer2 begin to wait !
Consumer1 begin to wait !
Produce1 produce:1
Consumer1 stop waiting !
Consumer1 consume:1
Consumer2 stop waiting !
Consumer2 begin to wait !
Produce2 produce:1
Consumer2 stop waiting !
Consumer2 consume:1
Consumer2 begin to wait !
Produce2 produce:1
Produce1 produce:2
Consumer1 consume:2
Consumer2 stop waiting !
Consumer2 consume:1
Consumer1 begin to wait !
Produce2 produce:1
Consumer1 stop waiting !
Consumer1 consume:1
Consumer2 begin to wait !
Produce1 produce:1
Produce1 stop at last !  

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Java生产者与消费者（下）