I'm looking for a KDTree implementation in Java.
I've done a google search and the results seem pretty haphazard. There are actually lots of results, but they're mostly just little one-off implementations, and I'd rather find something with a little more "production value". Something like apache collections or the excellent C5 collection library for .NET. Something where I can see the public bug tracker and check to see when the last SVN commit happened. Also, in an ideal world, I'd find a nice well-designed API for spatial data structures, and the KDTree would be just one class in that library.
For this project, I'll only be working in either 2 or 3 dimensions, and I'm mostly just interested in a good nearest-neighbors implementation.
In the book Algorithms in a Nutshell there is a kd tree implementation in java along with a few variations. All of the code is on oreilly.com and the book itself also walk you through the algorithm so you could build one yourself.