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

 /*
  * 这个例子用来解释多个生产者和多个消费者的情况
  */

 /*
  * 资源库
  */
 class Resource
 {
     private String name;
     private int count = 1;
     private boolean flag = false;
     public synchronized void set (String name){

         while (flag)
             try {this.wait();}
             catch(Exception e){

             }
             this .name = name + "--" + count++;
             System.out.println(Thread.currentThread().getName()+"生产商品"+this.name);
             flag = true;
             this.notifyAll();

         }

     public synchronized void out(){
         while (!flag)
             try {this.wait();}
             catch(Exception e){

             }
             System.out.println(Thread.currentThread().getName() + "消费了" + this.name);
             flag = false;
             this.notifyAll();
         }

     }

 /*
  * 生产者
  */
 class Producer implements Runnable
 {
     private Resource res;
     Producer (Resource res){

         this.res = res;
     }
     public void run(){

         while (true){

             res.set ("牙膏");
         }
     }

 }
 /*
  * 消费者
  */
 class Consumer implements Runnable
 {

     private Resource res;
     Consumer(Resource res){

         this.res = res;
     }
     public void run(){

         while (true){
             res.out();
         }
     }
 }
 public class producerConsumerDemo {

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         Resource res = new Resource();

         Producer p1 = new Producer(res);
         Producer p2 = new Producer(res);

         Consumer c1 = new Consumer(res);
         Consumer c2 = new Consumer(res);

         Thread t1 = new Thread(p1);
         Thread t2 = new Thread(p2);
         Thread t3 = new Thread(c1);
         Thread t4 = new Thread(c2);

         t1.start();
         t2.start();
         t3.start();
         t4.start();

     }

 }