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Java Timer

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 = new 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 IllegalStateException when I try to run a schedule call on a brand new Timer instance!?!?!?!

Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Task already scheduled or cancelled
    at java.util.Timer.sched(Unknown Source)
    at java.util.Timer.schedule(Unknown Source)
    at HelperTimer.setPeriod(



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;

        if (queue.getMin() == task)

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

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