Question

How to know if there is any scheduled timers currently?

There is TimerQueue to manage a queue of Timers, but all stuff is private or package private.

Thanks.

Answer 1

There is TimerQueue to manage a queue of Timers, but all stuff is private or package private.

Access modifiers don’t stop reflection. So you can do something like:

Timer t = new Timer();
TimerQueue tq = (TimerQueue) Timer.class.getField("queue").get(t);
boolean isEmpty = (Boolean) TimerQueue.class.getMethod("isEmpty").invoke(tq);

The member names were digged from JDK source code. Private stuff is not intended to be accessed this way, so this may break anytime. There’s no robust way to do this. It’s a pity that Timer doesn’t provide such API.