My colleagues and I recently do more investigation, we found the two alternatives for the byte array to string and vice versa:
1. sun.misc.BASE64Decoder and sun.misc.BASE64Encoder. But that was not officially supportted by SUN.
2. MigBase64 http://migbase64.sourceforge.net/.
Right now the MigBase64 is the fastest solution for this area. And detail bechmarch please check the url: http://migbase64.sourceforge.net/
So here means if you had direction, you could find any fastest solutions for you references.
The results is:
HEX encoder time:421371431 nano seconds
HEX decoder time:257492503 nano seconds
sun.misc.BASE64 encode time:258552414 nano seconds
sun.misc.BASE64 decode time:359357404 nano seconds
MigBASE64 encode time:49359904 nano seconds
MigBASE64 decode time:67830130 nano seconds
So you can see the average time for MigBase64 6 times faster than SunBase64 and 10 times faster than my proposed yesterday.