并发工具使用【CountDownLatch,CyclicBarrier】--代码示例

﹏ヽ暗。殇╰゛Y 2024-04-18 11:14 98阅读 0赞

##  1.CountDownLatch 的使用 ##

### 应用场景： ###

等待已知数量的线程执行完后 ，在唤醒当前的主线程的应用场景，比如：查询所有航空公司的机票，多个线程单独执行查询单个航空公司的机票，所有的单个线程结束后，环境主线程，将结果输出。

相当于计数器进行减的操作

### 实例代码： ###

package com.lhj;
    
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;
    import java.util.Random;
    import java.util.concurrent.CountDownLatch;
    import java.util.concurrent.TimeUnit;
    
    public class CountDownLatchDemo {
    
        //针对航班查询进行举例
    
        private static List<String> company = Arrays.asList("东方航空", "南方航空", "海南航空");
        private static List<String> fightList = new ArrayList<>();
    
        public static void main(String[] args) throws InterruptedException {
    
            String origin = "PEK";
    
            String dest = "pvg";
    
            Thread[] threads = new Thread[company.size()];
    
    
            CountDownLatch countDownLatch = new CountDownLatch(company.size());
    
            for (int i = 0; i < threads.length; i++) {
                final String companyName = company.get(i);
    
                threads[i] = new Thread(() -> {
                    System.out.println(companyName + "查询飞机票从"+origin+"到" + dest);
    
                    //随机产生票数
                    int paperNum = new Random().nextInt(10);
    
                    try {
                        TimeUnit.SECONDS.sleep(paperNum);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    fightList.add(companyName + "--" + paperNum);
                    System.out.printf("%s公司查询成功！\n", companyName);
                    countDownLatch.countDown();
                });
    
                threads[i].start();
    
            }
    
            countDownLatch.await();
            System.out.println("==============查询结果如下：================");
            fightList.forEach(System.out::println);
    
        }
    
    
    }

### 运行结果 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3MzA2MDQx_size_16_color_FFFFFF_t_70][]

## 2.CyclicBarrier的使用 ##

### 应用场景： ###

等待所有线程开启完成后，唤醒主线程，例如

等该所有参赛的运动员参赛全部到位后，开始比赛

相当于计数器进行加的操作

### 示例代码： ###

import java.util.Random;
    import java.util.concurrent.BrokenBarrierException;
    import java.util.concurrent.CyclicBarrier;
    import java.util.concurrent.TimeUnit;
    
    public class CyclicBarrierDemo {
    
    
        public static void main(String[] args) {
    
    
            Thread[] running = new Thread[8];
    
            CyclicBarrier cyclicBarrier = new CyclicBarrier(running.length);
    
    
            for (int i = 0; i < running.length; i++) {
                running[i] = new Thread(() -> {
                    try {
                        TimeUnit.SECONDS.sleep(new Random().nextInt(10));
                        System.out.println(Thread.currentThread().getName() + "准备好了！");
                        cyclicBarrier.await();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } catch (BrokenBarrierException e) {
                        e.printStackTrace();
                    }
    
                    System.out.println("选手" + Thread.currentThread().getName() + "起跑");
                }, "player" + i);
    
                running[i].start();
            }
    
        }
    }

### 运行结果： ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3MzA2MDQx_size_16_color_FFFFFF_t_70 1][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3MzA2MDQx_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/f3f28710b41949299dbb962457cd8595.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3MzA2MDQx_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/8eca3823fa1949848632f335d411b776.png