生产者和消费者问题

生产者和消费者是操作系统中的一个经典问题，这个问题是在讲“进程同步”时的一个例子，下面我就用Java语言中的notify和wait关键字实现这个算法。

生产者

public class Producer extends Thread
{
    static final int MAXQUEUE = 10;
    private Vector   messages = new Vector();
   
    @Override
    public void run() {
        try {
            while (true) {
                putMessage();
                sleep(1500);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    private synchronized void putMessage() throws InterruptedException {
        while (messages.size() == MAXQUEUE) {
            wait();
        }
        messages.add(new Date().toLocaleString());
        System.out.println("put message...");
        notify();
    }
    //Called by Consumer
    public synchronized String getMessage() throws InterruptedException {
        notify();
        while (messages.size() == 0) {
            wait();
        }
        String message = (String) messages.firstElement();
        messages.remove(message);
        return message;
    }
}

消费者

public class Consumer extends Thread
{
    Producer producer;
    Consumer(Producer p) {
        producer = p;
    }

    @Override
    public void run() {
        try {
            while (true) {
                String message = producer.getMessage();
                System.out.println("Got message: "+message);
                sleep(2000);
            }
        } catch(InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        Producer producer = new Producer();
        producer.start();
        new Consumer(producer).start();
    }
}

结果

put message...
Got message: 2016-11-5 17:06:28
put message...
Got message: 2016-11-5 17:06:30
put message...
Got message: 2016-11-5 17:06:32
put message...
put message...
Got message: 2016-11-5 17:06:33
put message...
Got message: 2016-11-5 17:06:35
put message...
Got message: 2016-11-5 17:06:36
put message...
put message...
Got message: 2016-11-5 17:06:38