I suspect this:
PATH=.:/usr/jdk/instances/jdk1.6.0_24
isn't right, and you need instead
PATH=.:/usr/jdk/instances/jdk1.6.0_24/bin
to pick up the binary directory within that Java installation.
p.s. I wouldn't put the current directory (.) in your PATH
. Otherwise someone can substitute a trojan-like program (e.g. a substitute for ls
) in a directory. You'll pick that up when you cd into the containing directory and type ls
(there's an entertaining story relating to this in the Unix Power Tools book)