How am I supposed to use the Thread Event Dispatch Event to call
from an Applet the function play() located in the MP3Player class ?It is giving me hard times to do it especially that I'm getting the songs from a JFileChooser
Firstly are you really sure you want to use the Event Dispatch Thread to do this and secondly unless you are specific about what the problem is how do you expect us to offer you to right advice.

With regard to the event dispatch thread, if you use it to create and play the MP3Player your GUI will effectively lock up until play completes, unless of course the MP3Player creates its own background thread to play the song.