Are Thread.sleep(0) and Thread.yield() statements equivalent?
No. The most obvious difference is that sleep() throws the (checked) InterruptedException. In practice, the effect may be almost the same, but it's entirely implementation-dependant.
I'd wager that doing each a million times in a row would take much longer for sleep(), since system timer granularity probably often causes it to actually sleep for a non-negligible amount of time.
Yield adds the current thread to the ready queue and allows other threads to run. Sleep is not guaranteed to relinquish the cpu.