Besides RoboVM [1], there are also other solutions, like Codename One [2] that's based on XMLVM [3], or Avian [4] which is a new and very promising lightweight VM that can also compile code to native. And there's also J2ObcC [5] a compiler that's being developed and used by Google to share code between Android and iOS.
You know, Java can be many things, but you can't beat its ecosystem ;-)