New to Java

I'm duplicating this topic: http://forums.sun.com/thread.jspa?threadID=5238294
I've the same problem after years, so why to lock, if there is no any solution.
I've downloaded svnant, and executed ant:

$ ant
Buildfile: build.xml

compile:
    [mkdir] Created dir: /home/kenorb/Downloads/ubuntu/svnant/build/classes
    [javac] Compiling 50 source files to /home/kenorb/Downloads/ubuntu/svnant/build/classes
    [javac] javac: invalid target release: ${targetJvm}
    [javac] Usage: javac <options> <source files>
    [javac] use -help for a list of possible options

$ javac -version
javac 1.6.0_0

How to check proper paths and set up this properly? I'm on Ubuntu.