After wait shoudln't thread be in blocking state rather than runnable state?

Question

Hi,

I am going through a java 6 book. A sample code snippet is given below from Threads chapter, where I need a clarification

synchronized(a){ //The thread gets the lcok on 'a'
a.wait(2000);// Thread releases the lock and waits for notify only for maximum of two seconds, then goes back to runnable state
//The thread reacquires the lock
//More instructions here
}

Now my doubt is, after 2 seconds of wait time, to continue further code execution, the above code would require the lock on object 'a' and there is fair chance that the other thread (which is supposed to call notify() on a) might already be holding a lock on it.

So shouldn't the thread go to Blocking state after 2seconds wait, instead of Runnable state as mentioned above in the comments (in Line No. 2).

Kindly clarify what am I missing here.

Thanks & Regards, Harish

Answer 1

If another thread has the lock on the object, then yes, you are correct, it will wait. The javadocs for wait state the following behavior when the specified amount of time elapses.

"The thread T is then removed from the wait set for this object and re-enabled for thread scheduling. It then competes in the usual manner with other threads for the right to synchronize on the object; once it has gained control of the object, all its synchronization claims on the object are restored to the status quo ante - that is, to the situation as of the time that the wait method was invoked"