Well google's guava library[1] has been on stackoverflow.com for a while and they encourage users to post question in stackoverflow rather than posing it to the google group[2].

"To get help on a specific question or problem, post a question to Stack Overflow with the tag "guava". We monitor these questions using this RSS feed.)"

1. https://code.google.com/p/guava-libraries/ 2. https://groups.google.com/group/guava-discuss/