1. CountDownLatch定義
一個同步輔助類,在完成一組正在其他線程中執行的操作之前,它允許一個或多個線程一直等待。
2.主要方法
public CountDownLatch(int count);
public void countDown();
public void await() throws InterruptedException
構造方法參數指定了計數值(count)實際上就是閉鎖需要等待的線程數量
countDown方法,當前線程調用此方法,則計數減一
await方法,調用此方法會一直阻塞當前線程,直到計時器的值爲0
3.例子
public class CountDownLatchDemo {
final static SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
public static void main(String[] args) throws InterruptedException {
CountDownLatch latch=new CountDownLatch(2);//兩個工人的協作
Worker worker1=new Worker("zhang san", 5000, latch);
Worker worker2=new Worker("li si", 8000, latch);
worker1.start();//
worker2.start();//
latch.await();//等待所有工人完成工作
System.out.println("all work done at "+sdf.format(new Date()));
}
static class Worker extends Thread{
String workerName;
int workTime;
CountDownLatch latch;
public Worker(String workerName ,int workTime ,CountDownLatch latch){
this.workerName=workerName;
this.workTime=workTime;
this.latch=latch;
}
public void run(){
System.out.println("Worker "+workerName+" do work begin at "+sdf.format(new Date()));
doWork();//工作了
System.out.println("Worker "+workerName+" do work complete at "+sdf.format(new Date()));
latch.countDown();//工人完成工作,計數器減一
}
private void doWork(){
try {
Thread.sleep(workTime);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
輸出:
Worker zhang san do work begin at 2011-04-14 11:05:11
Worker li si do work begin at 2011-04-14 11:05:11
Worker zhang san do work complete at 2011-04-14 11:05:16
Worker li si do work complete at 2011-04-14 11:05:19
all work done at 2011-04-14 11:05:19