CountDownLatch和CyclicBarrier

Posted 2020-11-02 意犹未尽

CountDownLatch

CountDownLatch是jdk5  java.util.concurrent新增的的工具类

使用场景。导出excel需要解析创建多个sheel。创建多线程并行执行。执行完毕 相应给客户端

public static void main(String[] args) throws InterruptedException {
        final java.util.concurrent.CountDownLatch countDownLatch=new CountDownLatch(2);
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                // TODO Auto-generated method stub
                System.out.println(Thread.currentThread().getName()+"解析数据并写入sheel");
                countDownLatch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                // TODO Auto-generated method stub
                System.out.println(Thread.currentThread().getName()+"解析数据并写入sheel");
                countDownLatch.countDown();
            }
        }).start();
        countDownLatch.await();
        System.out.println("响应给客户端");
    }

打印

Thread-0解析数据并写入sheel
Thread-1解析数据并写入sheel
响应给客户端

　　

await的线程会阻塞等待其他线程调用countDown 每调用一次number-1  直到为0   countDown 可以是多个线程 也可以是一个线程的多个步骤执行完毕

CyclicBarrier

CyclicBarrier跟CountDownLatch的区别

                        1.CountDownLatch是一个线程阻塞等待多个线程唤醒。 CyclicBarrier是阻塞多个线程直到多个线程调用await才继续往下执行

                        2.CountDownLatch计数器只能使用一次，CyclicBarrier可以使用多次 通过调用reset方法

public class CyclicBarrierTest implements Runnable {
	CyclicBarrier barrier;

	public CyclicBarrierTest(CyclicBarrier barrier) {
		this.barrier = barrier;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
	 System.out.println("讀取配置");
	 try {
		barrier.await();
	} catch (InterruptedException | BrokenBarrierException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
	 System.out.println("進行初始化");
	}

	public static void main(String[] args) {
		CyclicBarrier barrier=new CyclicBarrier(3);
		new Thread(new CyclicBarrierTest(barrier)).start();
		new Thread(new CyclicBarrierTest(barrier)).start();
		new Thread(new CyclicBarrierTest(barrier)).start();

	}

}

　　3个线程在执行读取完毕配置会等待其他线程都执行读取完毕后才往下执行