CountDownLatch线程等待使用教程

import java.util.concurrent.CountDownLatch;
public class WorkerExample {
public static void main(String[] args) throws InterruptedException {
int threadCount = 3;
CountDownLatch latch = new CountDownLatch(threadCount);
    for (int i = 1; i <= threadCount; i++) {
        final int taskId = i;
        new Thread(() -> {
            System.out.println("任务 " + taskId + " 开始执行");
            try {
                Thread.sleep(2000); // 模拟耗时操作
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
            System.out.println("任务 " + taskId + " 完成");
            latch.countDown(); // 任务完成，计数减一
        }).start();
    }

    System.out.println("主线程等待所有任务完成...");
    latch.await(); // 阻塞直到计数为0
    System.out.println("所有任务已完成，主线程继续执行");
}
}

import java.util.concurrent.CountDownLatch;
public class ConcurrentTest {
public static void main(String[] args) throws InterruptedException {
int userCount = 100;
CountDownLatch startSignal = new CountDownLatch(1);
CountDownLatch doneSignal = new CountDownLatch(userCount);
    for (int i = 0; i < userCount; i++) {
        new Thread(() -> {
            try {
                startSignal.await(); // 所有线程在此等待
                System.out.println(Thread.currentThread().getName() + " 发起请求");
                // 模拟请求处理
                Thread.sleep((long)(Math.random() * 1000));
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            } finally {
                doneSignal.countDown();
            }
        }).start();
    }

    Thread.sleep(2000); // 准备时间
    System.out.println("开始并发请求！");
    startSignal.countDown(); // 释放所有等待线程
    doneSignal.await();      // 主线程等待全部完成
    System.out.println("所有请求已完成");
}
}