java 并发模拟 工具类

以下是Java并发模拟工具类的介绍和示例：

1. CountDownLatch（线程计数器）
CountDownLatch是一个同步辅助类，它允许一个或多个线程等待其他线程完成操作后再继续执行。它通过一个计数器来实现，计数器的初始值可以设置为线程的数量，每个线程完成任务时，计数器的值减1，当计数器的值为0时，等待的线程将被唤醒。

import java.util.concurrent.CountDownLatch;

public class CountDownLatchDemo {
    public static void main(String[] args) throws InterruptedException {
        int threadCount = 5;
        CountDownLatch latch = new CountDownLatch(threadCount);

        for (int i = 0; i < threadCount; i++) {
            Thread thread = new Thread(new Worker(latch));
            thread.start();
        }

        latch.await(); // 等待所有线程完成任务

        System.out.println("All threads have completed their tasks.");
    }

    static class Worker implements Runnable {
        private final CountDownLatch latch;

        public Worker(CountDownLatch latch) {
            this.latch = latch;
        }

        @Override
        public void run() {
            // 模拟线程执行任务
            try {
                Thread.sleep(1000);
                System.out.println("Thread " + Thread.currentThread().getId() + " has completed its task.");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            latch.countDown(); // 完成任务后计数器减1
        }
    }
}

2. CyclicBarrier（回环栅栏）
CyclicBarrier是一个同步辅助类，它允许一组线程互相等待，直到所有线程都到达某个公共屏障点。当所有线程都到达屏障点后，屏障点上的任务将被执行。

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

public class CyclicBarrierDemo {
    public static void main(String[] args) {
        int threadCount = 3;
        CyclicBarrier barrier = new CyclicBarrier(threadCount, () -> {
            System.out.println("All threads have reached the barrier.");
        });

        for (int i = 0; i < threadCount; i++) {
            Thread thread = new Thread(new Worker(barrier));
            thread.start();
        }
    }

    static class Worker implements Runnable {
        private final CyclicBarrier barrier;

        public Worker(CyclicBarrier barrier) {
            this.barrier = barrier;
        }

        @Override
        public void run() {
            // 模拟线程执行任务
            try {
                Thread.sleep(1000);
                System.out.println("Thread " + Thread.currentThread().getId() + " has reached the barrier.");
                barrier.await(); // 等待其他线程到达屏障点
                System.out.println("Thread " + Thread.currentThread().getId() + " continues to execute.");
            } catch (InterruptedException | BrokenBarrierException e) {
                e.printStackTrace();
            }
        }
    }
}