Java并发工具：CountDownLatch和CyclicBarrier应用实例

原创傷城~ 2024-12-01 07:03 1阅读 0赞

CountDownLatch和CyclicBarrier是Java中两种常用的并发工具，它们在多线程场景中有着不同的功能。

1. CountDownLatch：
CountDownLatch用于一个或多个任务完成后通知其他任务。它有一个初始的计数值（countdown count），每个任务调用`await()`方法时会减少这个值，当计数值归零时，所有等待的任务都将被唤醒。

示例代码：

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

public class CountDownLatchExample {
    private final CountDownLatch latch = new CountDownLatch(3);

public void threadAction() throws InterruptedException {
        System.out.println("Thread " + Thread.currentThread().getName() + " is running");

try {
            latch.await();
            System.out.println("Thread " + Thread.currentThread().getName() + " has completed");
        } catch (InterruptedException e) {
            System.out.println("Thread " + Thread.currentThread().getName() + " interrupted");
            e.printStackTrace();
        }
    }

public static void main(String[] args) throws InterruptedException {
        CountDownLatchExample example = new CountDownLatchExample();

Thread t1 = new Thread(() -> example.threadAction()));
        Thread t2 = new Thread(() -> example.threadAction()));
        Thread t3 = new Thread(() -> example.threadAction()));

t1.start();
        t2.start();
        t3.start();

// 等待所有线程执行完毕
        t1.join();
        t2.join();
        t3.join();

System.out.println("All threads have completed execution");
    }
}
```

2. CyclicBarrier：
CyclicBarrier用于一组共享资源的多线程场景。当任意一个线程调用`await()`方法时，这个线程会阻塞，直到其他所有线程都调用了`countDown()`方法后，被阻塞的线程才会继续执行。

示例代码：

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

public class CyclicBarrierExample {
    private final CyclicBarrier barrier = new CyclicBarrier(2, "All threads have completed Barrier"));

public void threadAction() throws InterruptedException {
        System.out.println("Thread " + Thread.currentThread().getName() + " is running");

try {
            // 当前线程调用await()方法时，会阻塞
            barrier.await();

System.out.println("Thread " + Thread.currentThread().getName() + " has completed Barrier");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

public static void main(String[] args) throws InterruptedException {
        CyclicBarrierExample example = new CyclicBarrierExample();

Thread t1 = new Thread(() -> example.threadAction()));
        Thread t2 = new Thread(() -> example.threadAction()));

t1.start();
        t2.start();

// 等待所有线程执行完毕
        t1.join();
        t2.join();

System.out.println("All threads have completed execution");
    }
}
```

通过上述示例，你可以了解到CountDownLatch和CyclicBarrier在Java并发编程中的具体应用。