Hex to Decimal converter
Java's Integer class has a built-in method to parse a hex number (string) into an int:

Integer.valueOf("AB", 16)


W.R.T. your code, here are some observations:


hexRep should be final
Ideally your method should also accept lower-case text (just call toUpperCase() on the string)
Include some unit tests perhaps?
I wouldn't put that single method in a class of its own. More appropriate would be to put it in a more general utility class