I've done java development before but generally on windows (but I'm by no means an expert). 

I just want to set my CLASSPATH. When I run:

`echo $CLASSPATH`

(Is that right)? I get a empty line. So, it appears to me that my computer does not have a "Classpath" setup. What is the best practice to setup the classpath in Ubuntu (and linux in general)?

I'm using the default java for Ubuntu which should be OpenJDK. ~~Not sure it's important, but I want to use Rhino ([http://en.wikipedia.org/wiki/Rhino\_(JavaScript\_engine)](http://en.wikipedia.org/wiki/Rhino_%28JavaScript_engine%29))~~ *Note: I've been able to install Rhino via the package manager. There is both documentation and rhnio packages. Then, the commands are `js` and `rhino-debugger`*