Hi Mohit,
for AS-JAVA I would recommend this blog as first reading:
Single Sign-On for Java with SPNego.
For SPNEGO with AS ABAP I would recommend to start here:
For the ABAP part this forum is perfect because it is part of the SAP SSO product and it is well moderated by Donka Dimitrova.
Know How and discussions on AS JAVA are spread over SCN, most of it can probably be found in the portal corner.
Alway be aware the SPNEGO and Kerberos are used synonymously very often but Kerberos could also mean SNC-Configuration for GUI using Kerberos. This is a pitfall for "beginners".
Good luck!
Regards, Lutz