I've been trying to install Forge for a few days but when it's almost done it fails and says "Failed to run processor: java.io.EOFException:Unexpected end of ZLIB input stream" I've been trying to find help online but i don't know.
one class inside another, just like you have fields and methods inside of a class. ok, i admit it's not very intuitive now that type definitions are no longer a thing...
it doesn't have to be inner class, it can be a separate class. it's just more maintainable if you don't have two separate non-inner classes whose life cycles are connected.
just make both classes. serializer will make condition class instances when the game needs them.