I\'ve struggled a lot with Java but could not combine a working example of Java .wav to .mp3 converter. This converter will be used in a Java applet so it should depend only
If speed is not important for you, take any c implementation of MP3 (e. g. lame) and try to compile it with NestedVM to Java bytecode. It will be slow (like an emulator in an emulator), but it should work.
And it should be way less work than trying to port a MP3 library to pure Java.