BouncyCastle is a good implementation of the JCE. Its primarily a response to the stupid ITAR rules in the US that make it really difficult to export strong crypto. The rules have been made less draconian in recent years.
In the old rules, the US Department of Commerce assumed that only programmers in the US were smart and talented enough to write crypto code. So some companies were created outside the US to allow non-US programmers to make money selling crypto code.