CountDownLatchT.java

package org.javacore.concurrent;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * 同步辅助类:完成一组线程执行前,使得一个或多个线程一直等待
 *
 * Created by bysocket on 16/4/26.
 */
public class CountDownLatchT {

    // 线程中止的计数器
    private final static int COUNT = 10;
    private final static CountDownLatch count = new CountDownLatch(COUNT);

    // 线程池
    private final static ExecutorService service = Executors.newFixedThreadPool(5);

    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < COUNT; i++) {
            service.execute(() -> {
                try {
                    int time = new Random().nextInt(5);
                    TimeUnit.SECONDS.sleep(time);
                    System.out.printf("Thread %s ## 耗时:%d\n", Thread.currentThread().getId(), time);
                    // 线程结束后,计数器减一
                    count.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            });
        }

        // 主线程一直被阻塞,直到count为0,实现线程同步
        count.await();
        service.shutdown();

        System.out.println("同步线程执行组结束!");

    }
}