i would like to know that how can I communicate with my modem to answer
a phone call in java....
if anyone can send me the source then it'll be great but if one can
just tell me the basics of the process then it will be helpfull too....

Hi for that, as far as i know, u need to have some hardware boards like Intel
dialogic etc..
And for making calls through ur programs, to that board, u have to use some
speicific Dialogic-API's .In that you will have different board specific
functions avalilable like , make_call,play_message etc.......I am not sure..this
is relative to u or not.....