Problem installing rubymine-2.0.1

Hello everyone,

I have to install rubymine-2.0.1 for studies. My Operating System is Linux 9.10 Karmic Koala.

Iam not very experienced with Linux, so please explain all you steps in helping me install rubymine.
So it seems to me that their is an IDE integrated in rubymine ?
whatsoever, here is my problem:

First I downloaded the File

rubymine-2.0.1-tag.gz

into the DIR

/tmp

Then I exctracted it to the DIR

/tmp/rubymine93.95

Then I ran on the console:

cd /tmp/rubymine93.95/bin
sh ./rubymine.sh

In resulting with following error:

ERROR: cannot start RubyMine.
No JDK found to run RubyMine. Please validate either RUBYMINE_JDK or JDK_HOME points to valid JDK installation
exec: 60: /bin/java: not found

(Do you need more information ? I mean I can copy the code from the file rubymine.sh in here but I guess its likely uninteressting for you)

So I googled and found out that I have to point in the rubymine.sh file to the JDK...

So my Question how do I find out where JDK is installed ?
which line do I have to edit that it'll work ?

Thank you in advance for your help.

I stay tuned for feedback.

Thanks
Martin