Java多线程同步：CountDownLatch和CyclicBarrier示例

原创客官°小女子只卖身不卖艺 2024-09-14 16:54 74阅读 0赞

在Java多线程编程中，同步工具如CountDownLatch和CyclicBarrier是非常有用的。下面分别给出这两个类的使用示例。

1. CountDownLatch

CountDownLatch最初是一个单个计数器的实体，这个计数器可以被多个线程共同访问。

使用示例：
```java
import java.util.concurrent.CountDownLatch;

public class CounterExample {
    private CountDownLatch countDownLatch = new CountDownLatch(3);

public void workerThread(int index) {
        try {
            System.out.println("Worker thread " + index + " starting...");
            countDownLatch.countDown(); // Decrement count, allowing other threads to proceed
            System.out.println("Worker thread " + index + " finished.");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

public void main(String[] args) {
        Thread t1 = new Thread(() -> workerThread(0)));
        Thread t2 = new Thread(() -> workerThread(1)));
        Thread t3 = new Thread(() -> workerThread(2)));

t1.start(); // Start thread 1
        t2.start(); // Start thread 2
        t3.start(); // Start thread 3

try {
            countDownLatch.await(); // Wait for all count to reach zero
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
```
2. CyclicBarrier

CyclicBarrier是一个同步工具，它允许多个线程等待一个特定的阶段。

使用示例：
```java
import java.util.concurrent.CyclicBarrier;

public class BarrierExample {
    private CyclicBarrier barrier = new CyclicBarrier(3, "Finish!"));

public void workerThread(int index) {
        try {
            System.out.println("Worker thread " + index + " starting...");
            barrier.await(); // Wait for barrier to be reached
            System.out.println("Worker thread " + index + " finished.");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

t1.start(); // Start thread 1
        t2.start(); // Start thread 2
        t3.start(); // Start thread 3

try {
            barrier.await(); // Wait for all threads to reach barrier
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
```
以上两个示例展示了如何使用CountDownLatch和CyclicBarrier这两个Java多线程同步工具。