Question

Anybody know ,what is the logic behind Thread.sleep in java? . Are they using timer

Answer 1

Well, you can also take a look here http://openjdk.java.net. For ver. 7 there is some interesting code in jvm.cpp:

JVM_ENTRY(void, JVM_Sleep(JNIEnv* env, jclass threadClass, jlong millis))
  JVMWrapper("JVM_Sleep");


  if (millis osthread()->get_state();
      thread->osthread()->set_state(SLEEPING);
      os::sleep(thread, MinSleepInterval, false);
      thread->osthread()->set_state(old_state);
    }
  } else {
    ThreadState old_state = thread->osthread()->get_state();
    thread->osthread()->set_state(SLEEPING);
    if (os::sleep(thread, millis, true) == OS_INTRPT) {
      // An asynchronous exception (e.g., ThreadDeathException) could have been thrown on
      // us while we were sleeping. We do not overwrite those.
      if (!HAS_PENDING_EXCEPTION) {
        // TODO-FIXME: THROW_MSG returns which means we will not call set_state()
        // to properly restore the thread state.  That's likely wrong.
        THROW_MSG(vmSymbols::java_lang_InterruptedException(), "sleep interrupted");
      }
    }
    thread->osthread()->set_state(old_state);
  }
JVM_END