Authenticate and authorize users for my server

[bbc]

Hello,

I am looking for a way to serve information to my clients.  My clients are organized as groups of users that should have read/write access to data associated with their group but not other groups.  The client is an installed application (not a web page client).  I'm using Java.

Is it possible, or appropriate, to use their Google account to manage access to the data?  Should I be using OAuth 2.0?  

How would I organize multiple users into groups?  Is there an existing mechanism?

I'm a newbie, so any tips, links, recommendations and examples would be great!

Regards

bbc