在Java中如何使用CountDownLatch控制线程启动顺序_CountDownLatch线程顺序控制技巧解析

public class StartTogetherExample {
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch readyLatch = new CountDownLatch(1); // 控制启动信号

        for (int i = 1; i <= 3; i++) {
            final int threadId = i;
            new Thread(() -> {
                System.out.println("线程" + threadId + "已准备就绪，等待启动信号...");
                try {
                    readyLatch.await(); // 所有线程在此等待
                    System.out.println("线程" + threadId + "开始执行任务");
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }).start();
        }

        // 主线程模拟准备工作耗时
        Thread.sleep(2000);
        System.out.println("所有线程已准备完毕，发出启动信号！");
        readyLatch.countDown(); // 计数器减为0，释放所有等待线程
    }
}

CountDownLatch initComplete = new CountDownLatch(2); // 等待前两个线程初始化完成

Thread t1 = new Thread(() -> {
    System.out.println("T1 正在初始化...");
    try { Thread.sleep(1000); } catch (InterruptedException e) {}
    System.out.println("T1 初始化完成");
    initComplete.countDown();
});

Thread t2 = new Thread(() -> {
    System.out.println("T2 正在初始化...");
    try { Thread.sleep(1500); } catch (InterruptedException e) {}
    System.out.println("T2 初始化完成");
    initComplete.countDown();
});

Thread t3 = new Thread(() -> {
    System.out.println("T3 等待 T1 和 T2 初始化完成...");
    try {
        initComplete.await();
        System.out.println("T3 开始执行");
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }
});

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