As previously mentioned, the JSSE framework, along with the SunJSSE provider, implements the SSL and TLS protocol suites -- TLS being really just the newest version of SSL.

SSL uses public-key cryptography to exchange a set of shared keys, and then uses standard shared-key encryption to exchange data. The shared keys are used both for encrypting the data (making it unreadable by others) and for authenticating the data (ensuring that it hasn't come from an impostor).