java 中多线程之间的通讯之生产者和消费者 （多个线程之间的通讯）

在真实开发 中关于多线程的通讯的问题用到下边的例子是比较多的

不同的地方时if 和while 的区别 如果只是两个线程之间的通讯，使用if是没有问题的。

但是在多个线程之间就会有问题

  1 /*
  2  * 这个例子用来解释多个生产者和多个消费者的情况
  3  */
  4
  5 /*
  6  * 资源库
  7  */
  8 class Resource
  9 {
 10     private String name;
 11     private int count = 1;
 12     private boolean flag = false;
 13     public synchronized void set (String name){
 14
 15         while (flag)
 16             try {this.wait();}
 17             catch(Exception e){
 18
 19             }
 20             this .name = name + "--" + count++;
 21             System.out.println(Thread.currentThread().getName()+"生产商品"+this.name);
 22             flag = true;
 23             this.notifyAll();
 24
 25         }
 26
 27
 28     public synchronized void out(){
 29         while (!flag)
 30             try {this.wait();}
 31             catch(Exception e){
 32
 33             }
 34             System.out.println(Thread.currentThread().getName() + "消费了" + this.name);
 35             flag = false;
 36             this.notifyAll();
 37         }
 38
 39     }
 40
 41 /*
 42  * 生产者
 43  */
 44 class Producer implements Runnable
 45 {
 46     private Resource res;
 47     Producer (Resource res){
 48
 49         this.res = res;
 50     }
 51     public void run(){
 52
 53         while (true){
 54
 55             res.set ("牙膏");
 56         }
 57     }
 58
 59
 60 }
 61 /*
 62  * 消费者
 63  */
 64 class Consumer implements Runnable
 65 {
 66
 67     private Resource res;
 68     Consumer(Resource res){
 69
 70         this.res = res;
 71     }
 72     public void run(){
 73
 74         while (true){
 75             res.out();
 76         }
 77     }
 78 }
 79 public class producerConsumerDemo {
 80
 81     public static void main(String[] args) {
 82         // TODO Auto-generated method stub
 83         Resource res = new Resource();
 84
 85         Producer p1 = new Producer(res);
 86         Producer p2 = new Producer(res);
 87
 88         Consumer c1 = new Consumer(res);
 89         Consumer c2 = new Consumer(res);
 90
 91         Thread t1 = new Thread(p1);
 92         Thread t2 = new Thread(p2);
 93         Thread t3 = new Thread(c1);
 94         Thread t4 = new Thread(c2);
 95
 96         t1.start();
 97         t2.start();
 98         t3.start();
 99         t4.start();
100
101
102
103     }
104
105 }