That's a great question. While we only have the bandwidth to officially support three client drivers (we've internally developed the Python, Ruby, and JavaScript drivers), an enormous number of projects have sprung up to build drivers for everything from Go to C# / .NET, PHP, Haskell, Erlang, and more.
As far as a JVM-based client driver, kclay in this thread mentioned that he's been building a Scala driver that is compatible with 1.5, and will update it for 1.6. There's also a thread on Google Groups (https://groups.google.com/forum/?fromgroups#!topic/rethinkdb...) detailing some efforts on a Java driver to date.
If you're interested in contributing, shoot me an email at mike [at] rethinkdb.com. I'd love to see a Java driver happen, and we'll do everything we can to support such a project.
As far as a JVM-based client driver, kclay in this thread mentioned that he's been building a Scala driver that is compatible with 1.5, and will update it for 1.6. There's also a thread on Google Groups (https://groups.google.com/forum/?fromgroups#!topic/rethinkdb...) detailing some efforts on a Java driver to date.
If you're interested in contributing, shoot me an email at mike [at] rethinkdb.com. I'd love to see a Java driver happen, and we'll do everything we can to support such a project.