Welcome to the JavaRanch, Maze. Please change your displayed name to conform to our
naming policy. In short, your name must be a first name and last name, separated by a space and not obviously fake.
As for your question, document base and code base don't make sense in an application since there's no document (i.e. html file) loading the app.
java.io.File has a toURL() method which returns the URL representation of the file path, but I think you are barking up the wrong tree by using java.applet.AudioClip to play your media. The
Java Media Framework API will give you the kind of functionality that people expect in a media player, like the ability to display the length of a song.