Asynchronous Subprocess completion status

Asynchronous Subprocess completion status

I have a Task object which has to undergo several processing. The process
has many sub-processes taking Task from the input queue, process them and
place them in a output queue for the next subprocess. The process has
multiple processing path, and hence multiple exit points. I need some kind
of tracking mechanism to find out, processing of an Task object is
completed. For this, I have added a TaskWatch, which keeps the Task Id and
waits for notification from the exit points. Each exit point, after
completing its process, has to send a notification explicitly. Is there
any way / mechanism / pattern through which each exit point intimates the
TaskWatch about the completion. I am implementing it in Java.