Given a multi-threaded application, yield
will cause the currently executing thread to pause execution and be set in a waiting state. The JVM will then begin running another thread that was previously in a waiting state.
I believe the same thread that just yielded could technically be scheduled to start again.
And I have yet to see this in the wild though. So I think it is safe to avoid.
To elaborate:
In a multi-threaded environment threads are scheduled and unscheduled off and on at the JVM's will. So, even if yield is not called in code, your thread can/will automatically yield to other threads when the JVM decides it should. This allows multi-threading to work in an environment with only one processing core.
Calling yield simply tells the JVM to put the current thread in a waiting state even if the JVM wasn't going to.
I shall attempt an illustration:
The following is a very simplified illustration of the execution of 2 threads over time (assume 1 core)-
Thread\Time 1 2 3 4 5 6 7 8 9
Thread 1 ----------- ----- -------
Thread 2 ------- ---------- ------
Whenever you see a '-'
that means a thread is executing. A ' '
means that the thread is waiting. As you can see, only 1 thread can actually run at a time. So, while 1 runs, the other waits. What yield is intended to do is give other threads a chance to run ahead of the currently running thread.
public static native void yield();
:p – Donyadoodad