RE: [Avalon4:Fortress] Eating Crow (was Changes to RoleManager)

> From: Peter Royal [mailto:[email protected]]
> 
> On Thursday, December 12, 2002, at 02:08  PM, Berin Loritsch wrote:
> > 1) We should *never* explicitly throw a NullPointerException.
> >    If an argument is required, throw an IllegalArgumentException
> >    instead.  The meaning of the error is much more clear.
> 
> I'd actually prefer it the other way.. Why?
> 
> Throw a NullPointerException when an argument that is 
> expected is null.
> 
> Use IllegalArgumentException when there is an argument 
> supplied, but it 
> is invalid for other reasons.


When I see a NullPointerException coming from library code, I
instinctively think that there is a serious problem with the
*library* code and not my code.

Any time there is a contract for the incoming parameters, and
client code violates that contract, you should use the
IllegalArgumentException.  That lets the developer *using*
your software to know they are in violation of an expected
contract.

With the RoleEntry class, it is an explicit contract (i.e.
we are testing for the failure case) that no argument can
be null.  By using the IllegalArgumentException we don't
get any confusion over what the _source_ of the error is.