use of CRM_COND_COM_BADI badi... pls help

Hi fnds,

I am implementing ABAP routines to java user exits.

Now in abap routine, there is a select query from a z table. Now what i understood in developing the same in java user exit is --

download that same z table to crm from r3.

implement CRM_COND_COM_BADI badi, and right the select query there.

But what i dont understand is,

what ist he use of badi CRM_COND_COM_BADI ?

if i have a routine 615, where a z table is used..... how will it relate to this badi CRM_COND_COM_BADI, when i write a query..

basically that query is to tell whether the condition type shud execute or not in req routine...

now how can write this in badi?

I am totally confused with this badi, could u explain on how to write the query in a java user exit.

thanks a ton,

Niraja