Well, not quite unless you are actually using NetBeans. Can't say for sure about that - haven't quite gotten to the point with Java where I'm willing to jump there. But I do know when you try to start Alice by double clicking on alice.jar I get a "mainifest file not found" or something similar.

Caution : Do not do this at home unless you are willing to destroy your entire Alice setup - and maybe a few other things. Among other things, this may just demonstrate my talents - developed over nearly half a century - of being able to really screw up a computer.

However, the following link may be interesting:
http://ostermiller.org/opening_jar_files.html

Using this hint - and 7Zip on an XP machine (I haven't got it to work on Vista) - I was able to decompress the alice.jar file. Very nice - one can now see which compiled (.class) files are actually used in the version of Alice you are currently using.

Since, at least with a quick check, the uncompiled (.java) files are all available in the Alice source code listings, you - in PRINCIPLE - should be able to modify a .java file, recompile it and replace the original .class file with the new one.

Anyone that feels like it - have fun. But you were warned!