java.lang.Thread.sleep()
that occur inside loops.
Such calls are indicative of "busy-waiting". Busy-waiting is often inefficient, and may result in unexpected deadlocks as busy-waiting threads do not release locked resources.
Example:
class X { volatile int x; public void waitX() throws Exception { while (x > 0) { Thread.sleep(10);//warning: Call to 'Thread.sleep()' in a loop, probably busy-waiting } } }