I have recently started working on a Java based GeoJSON reader. It has the ability to read plain JSON, but this version creates Java objects for the various GeoJSON objects defined in the GeoJSON specification: coordinate, point, line, polygon, etc. This makes importing and using GeoJSON in a Java program much easier.
I’ve just committed an initial working version and I’m planning to update it in the near future. I would like to eventually add an easy way to build the GeoJSON objects and output them to a file as well.
Check out the project on GitHub.