Java并发：CountDownLatch、CyclicBarrier和 Semaphore

package com.cdinit;


import java.util.concurrent.CountDownLatch;



public class CountDownLatchDemo {
    public static void main(String[] arg) throws Exception{
       testLeave();
    }


    // 所有线程离开后，主线程才能离开
    public static void testLeave() throws Exception{
        CountDownLatch countDownLatch = new CountDownLatch(6);
        for (int i=1;i<=6;i++){
            new Thread(()->{
                System.out.println(Thread.currentThread().getName() + " 离开...");
                countDownLatch.countDown();
            },String.valueOf(i)).start();
        }
        countDownLatch.await();
        System.out.println(Thread.currentThread().getName() +"主线程离开...");
    }
}

package com.cdinit;

import java.util.concurrent.CyclicBarrier;

// 集齐七颗龙珠，召唤神龙
public class CyclicBarrierDemo {

    private static final int NUMBER = 7;

    public static void main(String[] ag) throws Exception{
        CyclicBarrier cyclicBarrier = new CyclicBarrier(NUMBER,()->{
            System.out.println("召唤神龙...");
        });

        for(int i=1;i<=7;i++){
            int tempInt = i;
            new Thread(()->{
                try {
                    System.out.println(Thread.currentThread().getName() + "收集了" + tempInt + "龙珠...");
                    cyclicBarrier.await();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            },String.valueOf(i)).start();
        }

    }
}

package com.cdinit;

import java.util.Random;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

public class SemaphoreDemo {
    public static void main(String[] arg) throws Exception{
        Semaphore semaphore = new Semaphore(3); // 3个停车位
        for(int i=1;i<=6;i++){
            // 模拟6个汽车
            new Thread(()->{
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName() + "号抢到车位...");
                    TimeUnit.SECONDS.sleep(new Random().nextInt(8));
                    System.out.println(Thread.currentThread().getName() + "号Leave离开车位...");
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    semaphore.release();
                }
            },String.valueOf(i)).start();
        }
    }
}