USB-Based Input for Java

So, I'm embarking on my first "real" Java project (er, so I want to do this in Java).  This project is in the form of an application that helps control inventory.  For every time the barcode on a box is scanned, the inventory count decrements by one.  I've got the algorithm and the arithmetic involved down.  I just don't know how to get the Java application to recognize USB input (such as something like a mouse).  So now I inquire: how would you go about doing this?

Thanks,
Angela Fox