I just found this really cool project called XMLVM.  This project is for converting code quickly and efficiently through XML.  First, it converts your code into XML and then it can convert it from XML to theoretically any language.

As of now, their biggest push is the Java to Objective-C for iPhone project.  They have completely created a cocoa touch implementation in Java so that you can program an iPhone application completely in Java and convert it.  They are also working on making it possible to convert Android applications to iPhone.  They have already displayed that this is possible to some extent, but it needs some more work to be completely finished.  As of now, they suggest only using the Android to iPhone for games.

You can find out more here.

Also, you can find some of their stories of success using this software here.