Joining a sleeping thread?

[Katrin Lüthi]

I came across a question where a Thread t is defined and started before a Thread s.
- Thread s calls t.join() (so the first Thread) as its first statement, afterwards it alternates between sleeping and printing some sequence (for loop).

- Thread t goes to sleep as his first statement, then prints out something and then alternates between sleeping and printing for some time (for loop)

To my knowledge, in this situation there's no guarantee that t will be running when s invokes t.join(), as the start sequence seems not to guarantee an order of execution. In this case, would s start anyway?

Moreover, in the Bates/Sierra book, it is stated that sleep actually helps threads taking turns - i.e. the other one could jump in while the first one sleeps.

In spite of all this, the solution to this question (LearnKey master exam) says that the order of printouts is ordered: first the ones from thread t, then the ones from thread s.
Am I missing something here?

[Paul Clapham]

You're making it way too complicated. When the thread s calls "t.join()", that means it waits for the thread t to finish. It doesn't matter what the thread t is doing -- sleeping, waiting, working, whatever -- thread s just doesn't do anything at all until thread t finishes.

[Ankit Garg]

yes and sleep gives other threads a chance to run when the other thread is runnable. in case of s, it is blocked by the call to join.
I think I am correct...I might have wrongly used the word blocked for thread s....