I did do some work on the Java API for the 0.10 release. So there are local and global Atomics. They can return values, or not, like the Scala interface. The Atomics can also be configured with a TransactionFactory like the Scala interface.

Docs showing where I got up to are at http://doc.akkasource.org/stm-java

There are also JUnit tests and examples in akka-actor/src/test/java

Great work Peter, closing this.