带有延迟的Java计时器永远不会运行

Question

I have java.util.Timer class and TimerTask to schedule, I want to do the task every day at 2AM.

My code:

public class AutomaticPuller {

    final private Timer t = new Timer();

    public AutomaticPuller() {
        Calendar today = Calendar.getInstance();
        today.set(Calendar.HOUR_OF_DAY, 2);
        today.set(Calendar.MINUTE, 0);
        today.set(Calendar.SECOND, 0);
        long cooldown = today.getTimeInMillis();
        if (today.getTime().before(new Date(System.currentTimeMillis()))) {
            cooldown += 24L*60L*60L*1000L;  
        }
        System.out.println("Task will run at: " + new Date(cooldown));
        TimerTask tt = new TimerTask() {
            public void run() {
                try {
                    updateAll();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        t.schedule(tt, cooldown, 24L*60L*60L*1000L);
    }
}

I see the output from println (Task will run at:) but the task that should run at 2AM is never executed, why ? I dont get it I have never met such a problem. No errors in output log.

Answer 1

Because you are using todays time in milliseconds as the delay in milliseconds before task is to be executed. That means the task will execute in about 47 years.

Answer 2

Fixed by adding this line:

cooldown = cooldown - System.currentTimeMillis();

Basically I just forgot to remove the current millis from the cooldown.