Brad Cox of Objective-C fame has written a preprocessor for Java (see Java+ Preprocessor).  The peculiarly unique piece about this preprocessor is the way it does Quasi-Literals. To learn more about Quasi-Literals head over to "Why Quasi-Literals?". 

Brad Cox adds a twist on Quasi-Literals, allowing for recursive applicaton based on user defined string pairs.  Take a look at the explanation, it handles multi-line strings and i18n quite cleanly.

Its a nice mechanism to keep in mind, just in case we upgrade the Java language.

Incidentally, Quasi-Literals are the proper abstractions to use for defining macros, in particularly Hygienic Macros.  JSE uses Quasi-Literals albeit with a different syntax.