How can I play music files in a java program?

[o_O]

MP3 is a bit of a format to avoid when it comes to Java, since it isn't natively supported. If you could sacrifice the MP3s for MIDI or WAV files, a quick and easy method you could include would be something like:

public AudioClip loadSound(String filename) {
   URL soundPath = getClass().getResource(filename);
   return Applet.newAudioClip(soundPath);
}

To access this method, just initialise a variable of type AudioClip, and pass the method the name or path of the string:

AudioClip sound = loadSound("hello.wav");

To start or stop the sound from playing:

sound.play();
sound.stop();

Also, note that to use this method, you need to import the java.net.* and java.applet.* packages.