Java并发工具如CountDownLatch和CyclicBarrier的使用示例

原创￡神魔★判官ぃ 2024-10-21 11:00 62阅读 0赞

CountDownLatch和CyclicBarrier是Java中两种常用的线程同步工具，它们主要用于控制多个线程的执行顺序。

1. CountDownLatch的使用示例：

```java
import java.util.concurrent.CountDownLatch;

public class CountDownLatchExample {
    public static void main(String[] args) {
        // 创建一个CountDownLatch，初始值为0
        CountDownLatch countDownLatch = new CountDownLatch(3);

// 创建三个线程，每个线程调用countDown方法减一
        Thread thread1 = new Thread(() -> countDownLatch.countDown()));
        Thread thread2 = new Thread(() -> countDownLatch.countDown()));
        Thread thread3 = new Thread(() -> countDownLatch.countDown()));

// 启动所有线程
        thread1.start();
        thread2.start();
        thread3.start();

// 等待CountDownLatch的计数变为0，表示所有任务都已经完成
        try {
            countDownLatch.await(5, TimeUnit.SECONDS));
            System.out.println("All tasks completed.");
        } catch (InterruptedException | TimeoutException e) {
            e.printStackTrace();
            System.out.println("Timeout occurred. Some tasks may not have finished.");
        }
    }
}
```

2. CyclicBarrier的使用示例：

```java
import java.util.concurrent.CyclicBarrier;

public class CyclicBarrierExample {
    public static void main(String[] args) {
        // 创建一个CyclicBarrier，初始值为0
        CyclicBarrier cyclicBarrier = new CyclicBarrier(3);

// 创建三个线程，每个线程调用barrier()方法等待下一个线程到达障碍点
        Thread thread1 = new Thread(() -> cyclicBarrier.await()));
        Thread thread2 = new Thread(() -> cyclicBarrier.await()));
        Thread thread3 = new Thread(() -> cyclicBarrier.await()));

// 启动所有线程
        thread1.start();
        thread2.start();
        thread3.start();

// 等待第一个线程到达障碍点，然后依次让其他线程到达
        try {
            cyclicBarrier.await(5, TimeUnit.SECONDS));
            System.out.println("Thread 1 reached barrier.");
            // 依次让其他线程到达
            cyclicBarrier.countDown();
            System.out.println("Thread 2 reached barrier.");
            cyclicBarrier.countDown();
            System.out.println("Thread 3 reached barrier.");
        } catch (InterruptedException | TimeoutException e) {
            e.printStackTrace();
            System.out.println("Timeout occurred. Some threads may not have finished.");
        }
    }
}
```

以上就是CountDownLatch和CyclicBarrier在Java并发编程中的基本使用示例。