Slightly OT: non-buffered stdin in Java

Under Java stdin (System.in) is a buffered stream not sent to the
application until return is pressed.  But, Java can read from
files/sockets and other generic InputStreams unbuffered.   So I was
wondering if there is a command that will make stdin go to a file so
that Java can open that file and read it unbuffered?

I know I can do something like cat ->file but that makes it hard to
sync stdout and stderr (both are unbuffered in Java) with the file
version of stdin

-- 
Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org