CountDownLatch實現計算線程阻塞

package com.thunisoft.countdownlatchExecutor;

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.Executor;

import java.util.concurrent.Executors;

public class CountDownLatchTest2 {

public static void main(String[] args) {

//初始化的countDownLatch值X一定和執行的線程數目（y）保持一致，會出現三種情況

//1.x>y導致countdown()方法的返回值不能--為0，導致await線程一致阻塞。程序無法結束

//2.x<y導致對這個線程集合沒有鎖住，導致await提前執行結束，導致，最後的結果信息不能保證什麼時候返回。

CountDownLatch latch = new CountDownLatch(20);

Executor executor = Executors.newFixedThreadPool(2);

List<threads> list = new ArrayList<>();

for (int i = 0; i < 9; i++) {

threads thread = new threads(i, latch);

executor.execute(thread);

list.add(thread);

}

try {

//線程阻塞，如果沒有把 CountDownLatch對象添加到監控的線程中，直接使用出現阻塞，不能執行下面sysout的代碼。

latch.await();

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

//此處可以添加任務對上麵線程執行結束的結果處理的方法代替sysout做出處理。

System.out.println("執行結束了");

}

}

class threads implements Runnable {

int x;

CountDownLatch latch;

public threads(int x, CountDownLatch latch) {

this.x = x;

this.latch = latch;

}

@Override

public void run() {

latch.countDown();

System.out.println(Thread.currentThread().getId() + "執行" + x);

}

}

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