CountDownLatch 自己的一點理解

package com.lyq.jsoup.MyQueue;

/**
 * Created by mike on 2016/12/19.
 */

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 * 示例：CountDownLatch的使用舉例
 * 構造方法參數指定了計數的次數
 * countDown方法，當前線程調用此方法，則計數減一
 * await方法，調用此方法會一直阻塞當前線程，直到計時器的值爲0
 */
public class TestCountDownLatch {
    private static final int N = 5;

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch startSignal = new CountDownLatch(1);//控制每一個線程是否開始
        CountDownLatch doneSignal = new CountDownLatch(N);

        for (int i = 1; i <= N; i++) {
            new Thread(new Worker(doneSignal, startSignal), "t" + i).start();//所有線程啓動,都處於等待狀態
        }

        System.out.println("begin------------");
        startSignal.countDown();//2:所有線程都執行
        doneSignal.await();//3:等待所有的線程執行完畢
        System.out.println("Ok");

    }

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

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

        public void run() {
            try {
                startSignal.await(); //1:等待開始執行信號的發佈
                System.out.println("thread name:" + Thread.currentThread().getName());
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                doneSignal.countDown();//4:每個線程一行完成，都會減一，知道doneSignal.count = 0
            }
        }
    }
}