Well forget Janino, use a compiled JAR format. Use something like Eclipse, Netbeans etc. to edit and modify your code and compile it. AFAIK SS's current Janino does not support generics.
To use compiled JAR files, you'll need to edit your mod_info file with a line like this:
"jars":["jars/my_code.jar"],
Using other an external IDE/compiler you can also hot update your code, and debug it on the fly. I highly recommend going down that path rather than relying on Janino to compile your code.