How does a synchronized statement work in this case?

You need the synchronized block around the loop.

Yes the synchronized statement you have will work like you expect it. I would just add one comment, the thread you are accepting socket connections will block on registry. Put(id, serverThread); while you are in the synchronized section on another thread.

This means that your server will not process any new incoming requests while you are processing the notification.....

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.