java 多線程之 CountDownLatch

CountDownLatch

閉鎖是一種同步工具類，可以延遲線程的進度直到其到達終止狀態；

countDwon 方法遞減計數器

await 方法等待計數器到達 0 ，爲 0 表示所有需要等待的事件都已經發生

代碼

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

public class CountDownLatchDemo implements Runnable{
    private static CountDownLatch end = new CountDownLatch(10);
    private static CountDownLatchDemo demo = new CountDownLatchDemo();

    @Override
    public void run() {
        try {
            Thread.sleep(new Random().nextInt(10)*1000);
            System.out.println("check complete!");
            end.countDown(); //通知 CountDownLatch 一個任務完成，執行 countDown
        }catch (InterruptedException e) { //中斷異常
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        ExecutorService exec = Executors.newFixedThreadPool(10);
        for (int i=0;i<10;i++){
            exec.submit(demo);
        }
        //等待檢查
        end.await();
        //發射火箭
        System.out.println("Fire !");
        exec.shutdown();
    }
}