Using Arduino with Java

Hello, I am new to Arduino and am thinking of purchasing one but need to check up on something first.

I have built a Java application which I am going to build into a physical installation and I want to be able to control it via a few buttons (I may yet do this using a dismantled Keyboard) but more importantly I have a couple of variable parameters that I want the users of the installation to control using levers. THese levers will connect to potentiometers using some cogs.

I am assuming that it will be a relatively trivial task to read in the input from these (via the arduino board and a USB interrface of course) and have them either change the parameters directly or call public methods in the java to do this.

Any ideas about how I go about this?

Many thanks