I just revised the ISBNValidator to support ISBN-13 / EAN-13 standards, which will begin its use on 2007 (see http://www.isbn.org/standards/home/isbn/transition.asp for more information).
To support a smooth transition, I changed the isValid(String) method so that it can validate all ISBN-10, ISBN-13 and EAN-13 codes. In addition, I created methods for validating only ISBN-10, only EAN-13, or ISBN-13 / EAN-13 codes. This way, anyone could have support for
the new standard by just changing the .jar file.
Please note that I've changed a few method names, and you may want to check the code style to match the existing one (however I tried to follow it whenever I could).