Java并发工具——CountDownLatch和Semaphore使用实例

原创 ╰+攻爆jí腚メ 2024-09-23 20:21 84阅读 0赞

CountDownLatch和Semaphore都是Java中的并发工具，用于控制多个线程的执行。下面是这两个工具的使用实例：

1. CountDownLatch（倒计数器）

当一个线程需要等待其他线程完成某项操作时，可以使用CountDownLatch来控制。

例如，一个生产者线程在生成商品后，需要通过CountDownLatch来等待消费者线程消费完商品后再释放计数。

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

public class CounterExample {
    private final CountDownLatch latch = new CountDownLatch(1);

public void producer() throws InterruptedException {
        System.out.println("Producer is generating product...");

// Generate product and wait for consumer to consume it.
        doProduct();
        
        System.out.println("Producer has released the latch.");
        latch.countDown();
    }

private void doProduct() {
        try {
            Thread.sleep(2000); // Simulate product generation time
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

public void consumer() throws InterruptedException {
        System.out.println("Consumer is waiting to consume the product...");

latch.await(); // Wait for producer to release the latch

System.out.println("Consumer has successfully consumed the product.");
    }

public static void main(String[] args) {
        CounterExample example = new CounterExample();
        
        Thread producerThread = new Thread(example::producer);
        Thread consumerThread = new Thread(example::consumer);

producerThread.start(); // Start producing
        consumerThread.start(); // Start consuming

try {
            producerThread.join(); // Wait for producer to finish
            consumerThread.join(); // Wait for consumer to finish
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

System.out.println("Program execution complete.");
    }
}
```

在这个例子中，生产者线程在生成商品后使用CountDownLatch等待消费者线程消费完商品。消费者线程通过await()方法在获取到计数器的值为0时开始消费产品。