How to choose java/javac 1.6

[ilantal]

I have a previous thread on a similar problem, but now it is well enough defined to ask a better question.
My main machine is Linux where I successfully compiled VTK. The problem is that I have both JDK 1.7 and 1.6 installed and I want to compile with 1.6. In VTK I see it is pointing to /usr/bin/java. If I go into the terminal I can see /usr, but I can't see it in Finder. Linux Nautilus has no such problem in that I can see everything.
In Linux I can look in /usr/lib/jvm and see all my java versions. There is no /usr/lib/jvm on the Mac, only usr/lib/java where I don't see anything which would allow me to choose. (It would also be nice if I had something with a GUI in place of the terminal to look at the disk contents.)
In /usr/bin/java -version I got version 1.7, so I need to find another java which will give a version of 1.6.

Thanks,
Ilan