Gpio programming

I'm a beginner in the beagleboard community.
I am working on interfacing a GM862 module with my beagleboard XM REV
C, so for starters I want to program the user button using java

Digest the info in these links below. For your userspace app, you
would probably want to look at the source code for evtest (as an
example of how a user app can read button events the gpio-key way) and
then translate to Java to do something similar in your application.

Basically, you have to insure your pinmux stuff is right first. If
you are only going to use the "user button" then it should work out of
the box but if you have to add more buttons ... that is where you have
to know how to verify or setup pin mux to do what you want. Then
register the gpio lines you want your buttons tied to. There are
basically two ways ... the gpio-keys way and the sysfs way.

Pinmux info: