Is it possible to play music in java from back to front?

Can't tell you how though, never tried.

you can look for some applet where a music file is attached

Completely doable, but I only have a theory of how. You'll need to control the flow of the raw bytes of sound sent to the output line and feed those bytes backwards. And I can tell you its more complicated than just reading the file in backwards, the whole thing may need to be processed before playback.