(I ended up writing ByteBuilder class called ByteBuf. A fast one that is easy to use.)
Question on StackOverFlow
The common answer seem to be to use ByteArrayBuffer, and I have used that on numerous occasions and it seems to work well. But... Since that answer was taken, and I have been hacking my own "language extensions for Java". I thought I would try a different approach.
Actual question on StackOverFlow