The Java Runtime Environment is the minimum standard Java Platform for 
running Java programs. It contains the Java virtual machine, Java core 
classes and supporting files.

Executables are installed into /usr/local/jdk1.1.8/bin. You may want to
put this into your PATH or symlink them to /usr/local/bin in case you
don't have kaffe installed (which shared many of the binarie's
names). 

You may want to build a kernel with
options         SYSVSEM

For more information about the Java for FreeBSD see
http://www.freebsd.org/java/

WWW: http://www.freebsd.org/java/