Akka in Scala, exclamation mark and question mark

Question

What is the difference between exclamation mark (!) and question mark (?) when sending messages to Actors?

myActor ! Hello(value1)
myAc         


        

Answer 1

Shamelessly copied [awesome] official doc (look Send messages section for more):

Messages are sent to an Actor through one of the following methods.

! means “fire-and-forget”, e.g. send a message asynchronously and return immediately. Also known as tell.

? sends a message asynchronously and returns a Future representing a possible reply. Also known as ask.