代碼如下

package Thread;
class Resource {
    private String name;
    private int count=0;
    private boolean flag=false;
    public synchronized void set(String name){
        while (flag){ //這裏必須用循環因為要讓每個生產者都知道自己要不要生產。如果不加就可能出現生產者喚醒生產者，然後連續兩次生產。
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        this.name=name+"--"+count++;
        System.out.println(Thread.currentThread().getName()+"...生產者..."+this.name);
        flag=true;
        this.notifyAll();//這裏也要用notifyAll()否則，可能造成所有的線程都在等待。
    }
    public synchronized void out(){
        while(!flag){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println(Thread.currentThread().getName()+"...消費者..."+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();
        }
    }
}
public class ProducterConsumerDemo {
    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();

    }
}

這是運行的結果。可以看出都是一個生產一個消費。

多線程之生產者和消費者模式