J2ObjC is not a Java emulator, but instead converts Java classes to Objective-C classes that directly use the iOS Foundation Framework. It supports the full Java 6 language and most of its runtime features that are required by client-side application developers, including exceptions, inner and anonymous classes, generic types, threads and reflection. JUnit test translation and execution is also supported. J2ObjC can be used with most build tools, including Xcode and Make.
I’m interested to try this out. Not because it is practical to use (there will be loads of places where the converter just won’t understand how Objective-C works), but because it is cool.