I'm sure you meant to say, "The return type can differ too..."
The return type of an overriding instance method or a hiding static method must be identical to the superclass method or you will get a compiler error.
I think that Ernest's point is that differing formal parameter types result in method overloading instead of overriding, while differing return types result in an error.
[ March 04, 2005: Message edited by: Mike Gershman ]