SystemClock.sleep() vs. Thread.sleep() while waiting for a semaphore loop

Question

In order to synchronize/queue access to a shared resource, I am about to use a Semaphore, aided by a wait loop.

In order not to run into CPU pegging, I would like to sleep() a little bit inside that while loop.

I searched the http://developer.android.com reference and found two such sleep() functions and I am confused as to which one fits which scenario:

1. Thread.sleep()
2. SystemClock.sleep()

Which one better suits the case I described and why?

Answer 1

First of all, do you really need a wait loop? You can typically solve your problems using proper notifications, i.e. having an Object, calling wait() and notify() on it or other means (like a blocking queue, or Semaphore.acquire() in your case).

That said, if you really want a polling loop (which you really shouldn't do unless you have to), I'd stick with Thread.sleep(). There's not much of a difference, as the documentation says, except that you have the option to interrupt a Thread.sleep(). Don't rid yourself the option to do so.

Note that in case of Thread.sleep(), you're going to have to catch that exception - if you're extremely lazy, you'll probably stick with SystemClock.sleep().