How do I use ProGuard?

Question

I was trying to learn how to use ProGuard, and it is no way as easy as I thought. At first I found a simple Java code to try it, a simple two class Swing calculator.

Answer 1

I've had similar problems, solved by taking out Java modifiers.

Java modifiers such as visibility modifiers are optional in the ProGuard configuration file -keep option (and in related options -keepclassmembers etc.)

From manual: -keep [,modifier,...] class_specification

So unless there is a specific reason otherwise, you can leave them out.