newbie - need help to control network interface

["Syed Md. Ashraful Karim" <ashraful ansur no>]

Hi All
I have just subscribed to the group. I want to choose (programmatically)
a network interface of my choice upon change of any network
configuration in the system. specially for mobile system. that is, 

- my code should be able to detect any network event changes (available
wireless, 3g, satellite network)
- among the possible active connections, it will choose one of my choice
- disable other connections, do not route any packet in that route.

ultimate goal is to choose the cheapest connection among (wireless, 3G,
Satellite IP etc.)

Is it possible to write Java code for this. or how can I program in
Linux? I would like to use Java library. Providing any good link or
documentation is appreciated. 

Thanks in advance.

regards,
ashraf.