CountDownLatch用法学习（一）

场景一：开启一个信号，用来阻止Worker线程在Driver准备就绪前执行。

package com.example.demo20181206;

import org.junit.Test;

import java.util.concurrent.CountDownLatch;

/**
 * @author xichengxml
 * @date 2018/12/7
 * @description
 */
public class CountDownLatchTest {

    @Test
    public void test() throws Exception{
        new Driver().main();
        Thread.sleep(10000);
    }

    class Driver {
        void main() throws InterruptedException {
            CountDownLatch startSignal = new CountDownLatch(1);
            CountDownLatch doneSignal = new CountDownLatch(10);

            // create and start threads
            for (int i = 0; i < 10; i++) {
                new Thread(new Worker(startSignal, doneSignal)).start();
            }
            System.out.println("I am doing something else..."); // don't let run yet
            startSignal.countDown(); // let all threads proceed
            System.out.println("I am still doing something else...");
            doneSignal.await(); // wait for all to finish
        }
    }

    class Worker implements Runnable {
        private CountDownLatch startSignal;
        private CountDownLatch doneSignal;

        public Worker(CountDownLatch startSignal, CountDownLatch doneSignal) {
            this.startSignal = startSignal;
            this.doneSignal = doneSignal;
        }

        public void run() {
            try {
                startSignal.await();
                System.out.println("I am working...");
                doneSignal.countDown();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}