To ensure platform independence, mobile programs are distributed in forms that are isomorphic to the original source code. Such codes are easy to decompile, and hence they increase the risk of malicious reverse engineering attacks. Code obfuscation is one of several techniques which has been proposed to alleviate this situation. An obfuscator is a tool which - through the application of code transformations - converts a program into an equivalent one that is more difficult to reverse engineer. In a previous paper  we have described the design of a control flow obfuscator for Java. In this paper we extend the design with transformations that obfuscate data structures and abstractions. In particular, we show how to obfuscate classes, arrays, procedural abstractions and built-in data types like strings, integers, and booleans.