Jhackernews is a project mainly written in Java, it's free.
A java library to access Hacker News site
A simple Java library that provides API to access contents of Hacker News (http://news.ycombinator.com/)
This library doesnt interface with HN directly, but instead uses the JSON APIs exposed by http://api.ihackernews.com/ site. Thanks to Ronnie Roller (http://ronnieroller.com/) for exposing these JSON APIs.