线程间交换信息的方式--JUC包中的并发工具

5.借助Java并发包中的并发工具，比如CountDownLatch、同步屏障CyclicBarrier、信号量Semphore

package edu.hubu.threadexchange;

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

/**
 * created by Sugar  2019/10/11 23:50
 */
public class JUCToolsDemo {
    public static void main(String[] args) {
        CountDownLatch countDownLatch = new CountDownLatch(1);
        List<String> list = new ArrayList<>();
        // 实现线程A
        Thread threadA = new Thread(() -> {
            for (int i = 1; i <= 10; i++) {
                list.add("abc");
                System.out.println("线程A向list中添加一个元素，此时list中的元素个数为：" + list.size());
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                if (list.size() == 5)
                    countDownLatch.countDown();
            }
        });
        // 实现线程B
        Thread threadB = new Thread(() -> {
            while (true) {
                if (list.size() != 5) {
                    try {
                        countDownLatch.await();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                System.out.println("线程B收到通知，开始执行自己的业务...");
                break;
            }
        });
        //　需要先启动线程B
        threadB.start();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 再启动线程A
        threadA.start();
    }

}