[603] in java-interest
Re: null objects and the instanceof operator
daemon@ATHENA.MIT.EDU (Simon Spero)
Thu Jul 6 13:21:19 1995
Date: Wed, 5 Jul 1995 20:58:10 -0700 (PDT)
From: Simon Spero <ses@tipper.oit.unc.edu>
To: java-interest@java.Eng.Sun.COM
On Wed, 5 Jul 1995, Nathan J. Williams wrote:
> For consistency, null needs to either be an instance of every
> class or of no class. I would prefer that null be an instance of no
> class. It is, in a sense, the language's only "non-object". More
> importantly, when the test:
> (a instanceof classB)
>
AS far as I can determine, java classes are all lifted domains, where
the object null is considered to be \bottom. If this were not the case,
then it would impossible to assign null to a variable of type <classB>.
Having (null instanceof C) be false would make things much more
complicated.
Since java has exceptions, it's much cleaner to either test for null, or
just perform the dereference and catch the exception.
Simon
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