Enthuware

I don't understand how catch block will be execute here ? i can't see any reason that will throw InterruptedException.

Right. It is not throwing InterruptedException. The assignment is after the catch block.
-Paul.

Thank you

what would be the answer if the assignment where in the catch block?

If the assignment were in the catch block, you would have to interrupt the hello thread while it is sleeping. You can do that by calling t.interrupt(); in main.
However, main may still fail to print 20 because the main thread could keep running and print 0 before the code for assignment gets to run.
So you could add t.sleep(2000); after t.interrupt() to see that assignment is done and then the value is printed.

You should try out various options to see how it works.

HTH,
Paul.