Are Thread.sleep(0) and Thread.yield() statements equivalent?

Question

Are these two statement equivalent?

Thread.sleep(0);
Thread.yield();

Answer 1

OpenJDK source (Java SE 7) have the following implementation for Thread.sleep(0) in JVM_Sleep function of jvm.cpp:

  if (millis == 0) {
    // When ConvertSleepToYield is on, this matches the classic VM implementation of
    // JVM_Sleep. Critical for similar threading behaviour (Win32)
    // It appears that in certain GUI contexts, it may be beneficial to do a short sleep
    // for SOLARIS
    if (ConvertSleepToYield) {
      os::yield();
    } else {
      ThreadState old_state = thread->osthread()->get_state();
      thread->osthread()->set_state(SLEEPING);
      os::sleep(thread, MinSleepInterval, false);
      thread->osthread()->set_state(old_state);
    }
  }

And implemtation of Thread.yield() have the following code:

  // When ConvertYieldToSleep is off (default), this matches the classic VM use of yield.
  // Critical for similar threading behaviour
  if (ConvertYieldToSleep) {
    os::sleep(thread, MinSleepInterval, false);
  } else {
    os::yield();
  }

So Thread.sleep(0) and Thread.yield() may call same system calls in some platforms.

os::sleep and os::yield are platform specific stuff. On both Linux and Windows: os::yield seems to be much simplier than os::sleep. For example: os::yield of Linux calls only sched_yield(). And os::sleep have about 70 lines of code.