How can I implement OAUTH2 authentication for Facebook in Java?

I have a Facebook Web app I wrote years ago using NetBeans that used Facebook Connect to authorize users. Later, Facebook changed their authentication scheme to OAuth2, but the NetBeans development team, for some reason, never updated the product to support authentication via OAuth2, so my app stopped working. 

I'm revisiting the issue in ordet to get my app up and running again. I read the Facebook docs and I think I know what to do, but I'm not sure what I need to remove from my app first. Has anyone else here dealt with this issue and if so, how should I proceed?