Programming Concurrency on the JVM

Actor Qualities

An actor is a free-running activity that can receive messages, process requests, and send responses. Actors are designed to support asynchrony and efficient messaging.

Each actor has a built-in message queue much like the message queue behind a cell phone. Both Sally and Sean may leave a message at the same time on Bob’s cell phone. The cell phone provider saves both their messages for Bob to retrieve at his convenience. Similarly, the actor library allows multiple actors to send messages concurrently. The senders are nonblocking by default; they send off a message and proceed to take care of their business. The library lets the designated actor sequentially pick its messages to process. Once an actor processes a message or ...