Java 8 Compatibility

Akka requires that you have Java 8 or later installed on your machine.

Starting with Akka 2.4.2 we have begun to introduce Java 8 types (most prominently java.util.concurrent.CompletionStage and java.util.Optional) where that was possible without breaking binary or source compatibility. Where this was not possible (for example in the return type of ActorSystem.terminate()) please refer to the scala-java8-compat library that allows easy conversion between the Scala and Java counterparts. The artifact can be included in Maven builds using:


We will only be able to seamlessly integrate all functional interfaces once we can rely on Scala 2.12 to provide full interoperability—this will mean that Scala users can directly implement Java Functional Interfaces using lambda syntax as well as that Java users can directly implement Scala functions using lambda syntax.

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