Java Timer

Question

I'm trying to use a timer to schedule a recurring event in an application. However, I want to be able to adjust the period at which the event fires in real time (according to the users input). For example: ``` public class HelperTimer extends TimerTask { private Timer timer; //Default of 15 second between updates private int secondsToDelay = 15; public void setPeriod(int seconds) { this.secondsToDelay = seconds; long delay = 1000; // 1 second long period = 1000*secondsToDelay; // seconds if (timer != null) { timer.cancel(); } System.out.println(timer); timer = new Timer(); System.out.println(timer); timer.schedule(this, delay, period); } public int getPeriod() { return this.secondsToDelay; } } ``` I then start a new instance of this class and call its set period function. However, when I do that, I get an Illegal state exception. You can see the System.out.println(timer); in there because I'm checking, and yep sure enough, they are two different timers... so why am I getting an Illega…

Accepted Answer

You can't reuse a TimerTask as you're doing here.

Relevant porition of Timer:

```
private void sched(TimerTask task, long time, long period) {
    if (time < 0)
        throw new IllegalArgumentException("Illegal execution time.");

synchronized(queue) {
        if (!thread.newTasksMayBeScheduled)
            throw new IllegalStateException("Timer already cancelled.");

synchronized(task.lock) {
            //Right here's your problem.
            //  state is package-private, declared in TimerTask
            if (task.state != TimerTask.VIRGIN)
                throw new IllegalStateException(
                    "Task already scheduled or cancelled");
            task.nextExecutionTime = time;
            task.period = period;
            task.state = TimerTask.SCHEDULED;
        }

queue.add(task);
        if (queue.getMin() == task)
            queue.notify();
    }
}
```

You'll need to refactor your code so that you create a new TimerTask, rather than re-using one.

Java Timer

Solution

Problem