深入理解Java并发工具：CountDownLatch和CyclicBarrier实战案例-蒲公英云

深入理解Java并发工具：CountDownLatch和CyclicBarrier实战案例

在Java的多线程编程中，CountDownLatch和CyclicBarrier是两个非常重要的并发工具。它们主要用于控制多个线程的执行顺序。

CountDownLatch

CountDownLatch是一种倒计时类型的对象，它的初始值至少为0。当一个线程等待某个事件发生（例如资源准备完毕）时，会将CountDownLatch的值减1。当所有需要等待的线程都完成了上述操作后，调用await()方法的线程才会继续执行。

实战案例：

import java.util.concurrent.CountDownLatch;
public class CountDownLatchExample {
    private static final int NUM_THREADS = 5;
    private static final int MAX_COUNT = NUM_THREADS * 2;
    public static void main(String[] args) throws InterruptedException {
        // 创建CountDownLatch对象，初始值为0
        CountDownLatch countDownLatch = new CountDownLatch(NUM_THREADS);
        // 创建并启动多个线程
        for (int i = 1; i <= NUM_THREADS; i++) {
            Thread workerThread = new Thread(() -> {
                try {
                    // 线程执行的任务，模拟等待资源准备完成
                    countDownLatch.await(MAX_COUNT);
                } catch (InterruptedException e) {
                    System.out.println("Thread " + i + " interrupted: " + e.getMessage());
                }
            }));
            workerThread.start();
        }
        // 当CountDownLatch的值减到0时，执行以下操作
        if (countDownLatch.getCount() == 0) {
            System.out.println("All threads finished waiting.");
            countDownLatch.countDown(); // 向所有等待线程发出计数为1的通知
        }
    }
}