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载;我们采取多线程操作,故中间要用sleep,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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