Java如何使用執行緒解決生產者消費者問題？

在Java程式設計中，如何使用執行緒解決生產者消費者問題？

以下範例演示如何使用執行緒解決生產者消費者問題。

package com.yiibai;

public class ProducerConsumerProblem {
    public static void main(String[] args) {
        CubbyHole c = new CubbyHole();
        Producer p1 = new Producer(c, 1);
        Consumer c1 = new Consumer(c, 1);
        p1.start();
        c1.start();
    }
}

class CubbyHole {
    private int contents;
    private boolean available = false;

    public synchronized int get() {
        while (available == false) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }
        available = false;
        notifyAll();
        return contents;
    }

    public synchronized void put(int value) {
        while (available == true) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }
        contents = value;
        available = true;
        notifyAll();
    }
}

class Consumer extends Thread {
    private CubbyHole cubbyhole;
    private int number;

    public Consumer(CubbyHole c, int number) {
        cubbyhole = c;
        this.number = number;
    }

    public void run() {
        int value = 0;
        for (int i = 0; i < 10; i++) {
            value = cubbyhole.get();
            System.out.println("Consumer #" + this.number + " get: " + value);
        }
    }
}

class Producer extends Thread {
    private CubbyHole cubbyhole;
    private int number;

    public Producer(CubbyHole c, int number) {
        cubbyhole = c;
        this.number = number;
    }

    public void run() {
        for (int i = 0; i < 10; i++) {
            cubbyhole.put(i);
            System.out.println("Producer #" + this.number + " put: " + i);
            try {
                sleep((int) (Math.random() * 100));
            } catch (InterruptedException e) {
            }
        }
    }
}

上述程式碼範例將產生以下結果 -

Producer #1 put: 0
Consumer #1 get: 0
Producer #1 put: 1
Consumer #1 get: 1
Producer #1 put: 2
Consumer #1 get: 2
Producer #1 put: 3
Consumer #1 get: 3
Producer #1 put: 4
Consumer #1 get: 4
Consumer #1 get: 5
Producer #1 put: 5
Producer #1 put: 6
Consumer #1 get: 6
Producer #1 put: 7
Consumer #1 get: 7
Producer #1 put: 8
Consumer #1 get: 8
Producer #1 put: 9
Consumer #1 get: 9