并发的三个工具类

package com.juc.ofok.demo;
import java.util.concurrent.CountDownLatch;
/**
 * 代码源于生活，高于生活
 *
 * @author ofok
 * @date 2020-04-19 18:45:33
 */
public class CountDownLatchDemo {
    /**
     *  有些任务是不得不阻塞的， 减法计数器
     */
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(6);
        for (int i = 0; i <= countDownLatch.getCount(); i++) {
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + " start ");
                // 出去一个人计数器就减 -1
                countDownLatch.countDown();
            }, String.valueOf(i)).start();
        }
        // 阻塞等待计数器归零
        countDownLatch.await();
        // 阻塞的操作：计数器 num++
        System.out.println(Thread.currentThread().getName() + " === END ");
    }
    /**
     *  结果诡异的嘛？达不到预期的 Main end 在最后一个
     */
    public static void test1() {
        for (int i = 1; i <= 6; i++) {
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+" start ");
            }, String.valueOf(i)).start();
        }
        System.out.println(Thread.currentThread().getName() + " End ");
    }
}

package com.ofok.juc.demo;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
/**
 * 代码源于生活，高于生活
 * 回环栅栏 计数器加法
 *
 * @author ofok
 * @date 2020-04-19 18:45:33
 */
public class CyclicBarrierDemo {
    public static void main(String[] args) {
        // 集齐7个龙珠召唤神龙 ++ 1//
        // 等待cyclicBarrier计数器满，就执行后面的Runnable，不满就阻塞
        CyclicBarrier cyclicBarrier = new CyclicBarrier(7, new Runnable() {
            @Override
            public void run() {
                System.out.println("神龙召唤成功！");
            }
        });
        for (int i = 1; i <= 7; i++) {
            final int temp = i;
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + "收集了第" + temp + "颗龙珠");
                try {
                    cyclicBarrier.await();
                    // 等待 阻塞
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }, String.valueOf(i)).start();
        }
    }
}

package com.ofok.juc.demo;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
/**
 * 代码源于生活，高于生活
 * 信号量（信号灯） 抢车位
 *
 * @author ofok
 * @date 2020-04-19 18:45:33
 */
public class SemaphoreDemo {
    public static void main(String[] args) {
        // 模拟6个车，只有3个车位
        // 3个位置
        Semaphore semaphore = new Semaphore(3);
        for (int i = 1; i <= 6; i++) {
            new Thread(() -> {
                // 得到车位
                try {
                    semaphore.acquire(); // 得到
                    System.out.println(Thread.currentThread().getName() + "抢到了车位");
                    TimeUnit.SECONDS.sleep(3);
                    System.out.println(Thread.currentThread().getName() + "离开了车位");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    // 释放位置
                    semaphore.release();
                }
            }, String.valueOf(i)).start();
        }
    }
}