SteamKit-Java
SteamKit-Java, is a java port of a library written for interfacing directly with various parts of the Steam network.
The major connection functionality exists, but there are plenty of functions I haven't tested yet.
You must include bouncycastle as a dependency to allow encryption of the packets.
Make sure you install the JCE.
You can test it with:
System.out.println(Cipher.getMaxAllowedKeyLength("AES"));
If that prints 128, you don't have JCE installed properly and a test will fail.
I'm too lazy to compile all of that crap
Check the Releases Section