Java并发程序设计(16)并发锁之条件变量

 

package com.test.concurrence;

 

import java.util.concurrent.locks.Condition;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

 

public class ConditionTest {

 

static  class  Worker {

public void work(int  who ,int next, int count){

//获取锁

lock.lock();

try {

 //等待条件成立：turn等于who

  while(who != turn){

 try {

condition.await();

} catch (InterruptedException e) {

e.printStackTrace();

}  

  }

 

  //条件已满足，开始做要做的事情

  for(int i=0;i<count;i++){

  System.out.println( who +  " : running " + i + " / " + count );

  }

 

  //暂停1秒。

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

 

  //改变条件。

  turn =  next;

  //通知下一个工人开始工作。

  condition.signal();

 

}finally{

//释放锁。

lock.unlock();

}

 

 

}

 

//所使用的锁。

private Lock       lock  = new  ReentrantLock();

//条件变量。

private Condition  condition  = lock.newCondition();

//条件要监控的变量。

private  volatile  int  turn = 0;

 

}

 

public static void main(String[] args) {

 

final int WORKER_A = 0;

final int WORKER_B = 1;

final int COUNT = 10;

final Worker  worker = new Worker();

new Thread( new Runnable(){

@Override

public void run() {

while(true){

worker.work( WORKER_A, WORKER_B, COUNT);

}

}

}).start();

 

new Thread( new Runnable(){

@Override

public void run() {

while(true){

worker.work( WORKER_B, WORKER_A, COUNT);

}

}

}).start();

 

 

}

 

}