How to know if other threads have finished?

Question

I have an object with a method named StartDownload(), that starts three threads.

How do I get a notification when each thread has finished executing?

Answer 1

I would suggest looking at the javadoc for Thread class.

You have multiple mechanisms for thread manipulation.

• Your main thread could join() the three threads serially, and would then not proceed until all three are done.

• Poll the thread state of the spawned threads at intervals.

• Put all of the spawned threads into a separate ThreadGroup and poll the activeCount() on the ThreadGroup and wait for it to get to 0.

• Setup a custom callback or listener type of interface for inter-thread communication.

I'm sure there are plenty of other ways I'm still missing.