在所有后台线程池线程完成时得到通知

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.CountDownLatch;

public class Main {
    public static void main(String[] args) throws InterruptedException {
        int numberOfThreads = 5;
        ExecutorService executorService = Executors.newFixedThreadPool(numberOfThreads);
        CountDownLatch countDownLatch = new CountDownLatch(numberOfThreads);

        for (int i = 0; i< numberOfThreads; i++) {
            executorService.execute(() -> {
                try {
                    // 这里是您的任务代码
                    System.out.println("Thread " + Thread.currentThread().getId() + " is running");
                } finally {
                    countDownLatch.countDown();
                }
            });
        }

        // 当所有线程完成时，countDownLatch的值为0
        countDownLatch.await();
        System.out.println("All threads are finished");

        executorService.shutdown();
    }
}