Java 根据不同的userId启动倒计时的定时任务（多线程）（两种方式）

1：使用java.util.Timer和java.util.TimerTask来实现倒计时的定时任务

import java.util.Timer;
import java.util.TimerTask;

public class CountdownTimer {
    private Timer timer;

    public CountdownTimer() {
        timer = new Timer();
    }

    public void startCountdown(long userId, int seconds) {
        TimerTask task = new TimerTask() {
            int remainingSeconds = seconds;

            @Override
            public void run() {
                if (remainingSeconds > 0) {
                    System.out.println("User " + userId + ": " + remainingSeconds + " seconds remaining.");
                    remainingSeconds--;
                } else {
                    System.out.println("User " + userId + ": Countdown finished.");
                    cancel(); // 倒计时完成后取消任务
                }
            }
        };

        timer.schedule(task, 0, 1000); // 每隔1秒执行一次任务
    }

    public static void main(String[] args) {
        CountdownTimer countdownTimer = new CountdownTimer();

        // 启动倒计时任务，倒计时10秒，userId为1
        countdownTimer.startCountdown(1, 10);

        // 启动倒计时任务，倒计时5秒，userId为2
        countdownTimer.startCountdown(2, 5);
    }
}

2：使用ScheduledExecutorService实现倒计时定时任务，更加灵活，推荐

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class CountdownTimer {
    private ScheduledExecutorService executorService;

    public CountdownTimer() {
        executorService = Executors.newScheduledThreadPool(5); // 创建线程池，可以根据需要调整线程池大小
    }

    public void startCountdown(long userId, int seconds) {
        Runnable task = new Runnable() {
            int remainingSeconds = seconds;

            @Override
            public void run() {
                if (remainingSeconds > 0) {
                    System.out.println("User " + userId + ": " + remainingSeconds + " seconds remaining.");
                    remainingSeconds--;
                } else {
                    System.out.println("User " + userId + ": Countdown finished.");
                    executorService.shutdown(); // 倒计时完成后关闭线程池
                }
            }
        };

        executorService.scheduleAtFixedRate(task, 0, 1, TimeUnit.SECONDS); // 每隔1秒执行一次任务
    }

    public static void main(String[] args) {
        CountdownTimer countdownTimer = new CountdownTimer();

        // 启动倒计时任务，倒计时10秒，userId为1
        countdownTimer.startCountdown(1, 10);

        // 启动倒计时任务，倒计时5秒，userId为2
        countdownTimer.startCountdown(2, 5);
    }
}