CountDownLatch

每次当线程调用countDownLatch.countDown()方法时，会对计数器减1，减到0，countDownLatch.await()放行

public class CountDownLatchTest {

    public static void main(String[] args) {

        CountDownLatch count = new CountDownLatch(7);
        for (int i=0; i < 7; i++){
            final int tempInt = i;
            new Thread(()->{
                System.out.println("线程"+tempInt+"执行");
                count.countDown();

            },String.valueOf(i)).start();
        }
        try {
            count.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("主线程开始执行");
    }
}

 

CyclicBarrier

与上面相反，当await()累计达到n次时，执行runnable 接口的线程。

public class CyclicBarrierTest {
    public static void main(String[] args) {
        CyclicBarrier cyc = new CyclicBarrier(7,()->{
            System.out.println("一切就绪");
        });

        for (int i=0; i < 7; i++){
            final int tempInt = i;
            new Thread(()->{
                System.out.println("线程"+tempInt+"执行");
                try {
                    cyc.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            },String.valueOf(i)).start();
        }
    }
}