Im working with Netbeans. Im using BasicPlayer 3.0 libs, to play a song, it plays fine when a run project with Netbeans BUT once a have my .jar file (with my lib folder and basicplayer3.0 jars) when a run my .jar project, mp3 song NEVER plays.
In all likelihood, your application is not finding the mp3 file/resource from within the jar. If your mp3 file is held inside of the jar file, then you cannot access it as a file, but rather as a resource, and the path to the resource is different from that of a file. For a resource, the path will be relative to your class files.
For more help, show us the code where you obtain and try to use your mp3 file.