Java主线程等待子线程执行完毕-CountDownLatch

主线程：

 

//Main主线程

public class MainThread {

 

    public static void main(String[] args) throws InterruptedException {

        long startTime = System.currentTimeMillis();

        int threadNum = 5; //线程数

        //定义正在运行的线程数

        CountDownLatch runningThreadNum = new CountDownLatch(threadNum);

        System.out.println(Thread.currentThread().getName()+"-start");

        //创建多个子线程

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

            new SubThread(runningThreadNum).start();

        }

        //等待子线程都执行完了再执行主线程剩下的动作

        runningThreadNum.await();

        System.out.println(Thread.currentThread().getName()+"-end");

        long endTime = System.currentTimeMillis();

        System.out.println("runningTime:"+(endTime-startTime));

    }

}

 

子线程：

//子线程

public class SubThread extends Thread{

 

    //子线程记数器,记载着运行的线程数

    private CountDownLatch runningThreadNum;

 

    public SubThread(CountDownLatch runningThreadNum){

        this.runningThreadNum = runningThreadNum;

    }

     

    @Override

    public void run() {

        System.out.println(Thread.currentThread().getName()+"-start");

        System.out.println(Thread.currentThread().getName()+"-do something");

        System.out.println(Thread.currentThread().getName()+"-end");

        runningThreadNum.countDown();//正在运行的线程数减一

    }

}