What kinds of problems might there be in writing an app for
deployment on desktop and PDA and cellphone simultaneously? I know
that people normally pick one platform and write for that. But what
if you wanted to use multiple specs, such as J2EE and J2ME/CDC and
J2ME/CLDC, all at the same time?

For example, I want to write a game that will run in a browser, on a
PDA, and on a cellphone. Some of the logic will obviously differ,
namely the UI. But some of the logic will be the same and I'd like
to write that part just once. Then at compile time, I want to
specify which platform to compile for without a lot of (or any) back-
end hacks.

So far, I'm using both the J2EE and J2ME versions of Sun ONE Studio.
The best I can think of at the moment is segment the code into
separate source files based on the libraries they use, then pull
them together differently in the respective IDEs. Is there any
easier way to do this? Is it possible to do this in a single IDE?