Java主线程等待子线程执行完毕-CountDownLatch

主线程：

 

//Main主线程
publicclassMainThread {

    publicstaticvoid main(String[] args) throwsInterruptedException {
        longstartTime = System.currentTimeMillis();
        intthreadNum = 5;//线程数
        //定义正在运行的线程数
        CountDownLatch runningThreadNum = newCountDownLatch(threadNum);
        System.out.println(Thread.currentThread().getName()+"-start");
        //创建多个子线程
        for(inti = 0; i < threadNum; i++) {
            newSubThread(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");
        longendTime = System.currentTimeMillis();
        System.out.println("runningTime:"+(endTime-startTime));
    }
}

 

子线程：

 

//子线程
publicclassSubThread extendsThread{

    //子线程记数器,记载着运行的线程数
    privateCountDownLatch runningThreadNum;

    publicSubThread(CountDownLatch runningThreadNum){
        this.runningThreadNum = runningThreadNum;
    }

    @Override
    publicvoidrun() {
        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
    }
}