DroidKit Actors is simple actor model implementation for java and Android
Jetlang provides a high performance java threading library. It is a complement to the java.util.concurrent package introduced in 1.5 and should be used for message based concurrency similar to event based actors in Scala.
Deprecated Actors Library for Scala
In-process Asynchronous Message System in Java for Event Bus/Actor Model (like Kilim, µJavaActors, Akka,... but very simplified)