I'm using JSSE in order to implement SSL. I understand that SSL in JSSE uses RSA.
Actually I find that only the first call to connect is really slow and all the other calls are much faster. I think the reason is that the HotSpot VM needs some time to compile the bytecode which is later executed.
There are several other JCE providers in the market but performance of RSA cipher almost the same. Actually there are only about 100 bytes ciphered by the RSA cipher and this is done only during the initial handshake time. The real data streams are ciphered using symmetric ciphers like DES or Blowfish which are much faster.