How to implement a countdown-triggered task in Java?

One common way to implement a countdown triggering task in Java is by using the Timer and TimerTask classes. The Timer class is used to schedule tasks to be executed at a specified time or at fixed time intervals, while the TimerTask class is an abstract class that represents a task that can be scheduled by the timer to be executed once or repeatedly.

Here is an example code using Timer and TimerTask to implement a countdown trigger task:

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

public class CountdownTriggerTask {
    public static void main(String[] args) {
        int countdownSeconds = 10; // 倒计时秒数

        TimerTask task = new TimerTask() {
            int remainingSeconds = countdownSeconds;

            public void run() {
                if (remainingSeconds > 0) {
                    System.out.println("倒计时 " + remainingSeconds + " 秒");
                    remainingSeconds--;
                } else {
                    System.out.println("任务触发");
                    // 执行触发任务的操作
                    cancel(); // 倒计时结束后取消任务
                }
            }
        };

        Timer timer = new Timer();
        timer.scheduleAtFixedRate(task, 0, 1000); // 每秒执行一次任务
    }
}

The code above first defines an anonymous inner class TimerTask, which overrides the run method to update the remaining seconds each time the task is executed and to perform the trigger task when the countdown ends. Then, a Timer instance is created, and the scheduleAtFixedRate method is used to schedule the task to start executing after 0 seconds and repeat every 1 second interval. The time interval can be adjusted as needed.

In actual application, it may be necessary to perform certain operations when a task is triggered, which can be done by adding the corresponding code in the run method of TimerTask.