countDownLatch 使用

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;

/**
 * Created by bjchengpeng on 2017/9/25.
 */
public class Test {

    public static void main(String [] args){
        // 用来测试的List
        List<String> data = new ArrayList<>();
        System.out.println(data.size());
        // 用来让主线程等待100个子线程执行完毕
        CountDownLatch countDownLatch = new CountDownLatch(100);
        // 启动100个子线程
        for(int i=0;i<10000;i++){
            SampleTask task = new SampleTask(data,countDownLatch);
            Thread thread = new Thread(task);
            thread.start();
        }
        try{
            // 主线程等待所有子线程执行完成，再向下执行
            countDownLatch.await();
        }catch (InterruptedException e){
            e.printStackTrace();
        }
        // List的size
        System.out.println(data.size());
    }
}
class SampleTask implements Runnable {
    CountDownLatch countDownLatch;
    List<String> data;
    public SampleTask(List<String> data,CountDownLatch countDownLatch){
        this.data = data;
        this.countDownLatch = countDownLatch;
    }
    @Override
    public void run() {
        // 每个线程向List中添加100个元素
        for(int i = 0; i < 100; i++)
        {
            data.add("1");
        }
        // 完成一个子线程
        countDownLatch.countDown();
    }
}

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;

/**
 * Created by bjchengpeng on 2017/9/25.
 */
public class Test2 {


    public static void main(String[] args) {
        // 用来测试的List
//        List data = Collection.(new ArrayList());
//        List<String> data = new ArrayList<>();

        List<String> data = Collections.synchronizedList(new ArrayList());


        // 用来让主线程等待100个子线程执行完毕
        CountDownLatch countDownLatch = new CountDownLatch(100);
        // 启动100个子线程
        for (int i = 0; i < 10000; i++) {
            SampleTask2 task = new SampleTask2(data, countDownLatch);
            Thread thread = new Thread(task);
            thread.start();
        }
        try {
            // 主线程等待所有子线程执行完成，再向下执行
            countDownLatch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // List的size
        System.out.println(data.size());
    }
}

class SampleTask2 implements Runnable {
    CountDownLatch countDownLatch;
    List<String> data;

    public SampleTask2(List<String> data, CountDownLatch countDownLatch) {
        this.data = data;
        this.countDownLatch = countDownLatch;
    }

    @Override
    public void run() {
        // 每个线程向List中添加100个元素
        for (int i = 0; i < 100; i++) {
            data.add("1");
        }
        // 完成一个子线程
        countDownLatch.countDown();
    }

}