Hi there,
I'm trying to develop my first game for Windows and Android.
After reading a bit about available options i decided that for those given platforms the best choice would be Java + libgdx.
As for my first 2d game it will be simple clone of Missile Command :-).

For now I have some missiles which can be launched to a specific target location (mouse click) with certain speed in pixels/second.
After the missile reaches target it creates Explosion object (Actor) on the screen in given location and the Explosion itself grows until max radius is reached.

I would like to detect collisions between 2 pairs of objects Explosion <-> EnemyMissile and EnemyMissile <-> Building.

I found some tutorials suggesting extending class b2ContactListener in here:
http://blog.allanbishop.com/box2d-2-1a-tutorial-%E2%80%93-part-4-collision-detection/
and
http://box2d.org/forum/viewtopic.php?f=8&p=27546#p27546

But I can't find the b2ContactListener, b2World etc...

Can someone point me to a tutorial or some sources using collision detection in Java with libgdx?

If any more info is needed from my side, please let me know.

Regards
Afesh