Dave Sifry http://en.wikipedia.org/wiki/Technorati

Technorati is a popular website that essentially indexes, sorts, and categorizes blogs.

You first need to register and open an account on Technorati. Then you can claim a blog and connect it to your account.
You'll be asked to put a line of code/link on your blog so that Technorati can register/verify it as your blog.

You can search any blogs directory (e.g. technorati) for blogs in a certain area, in this case about Java.

There are many blog directories that offer lists of blogs by categories. You can try Technorati or many others.