This is not the same as the class of all null classes
2.
So what exactly is the Russellian null class?
3.
This null class-of-classes
4.
%: the class of all null classes is destined to become " 0 "; see below.
5.
Note, that NOT having a null class at all is an important feature, in contrast to languages where " anything is a reference " ( e . g.
6.
As with C + +, a null class can be instantiated in situations where a reference to an Animal object is required, but there is no appropriate object available.
7.
But this is visually confusing, especially with regards to the null class, so a dashed vertical line at each end of the collection will be used to symbolize the collection-as-aggregate:
8.
As with C + + and related languages, that special null class must be created for each class hierarchy that needs a null object, since a NullAnimal is of no use when what is needed is a null object that does not implement the Animal interface.
9.
The special null class must be created for each class hierarchy that is to have a null object, since a null _ animal is of no use when what is needed is a null object with regard to some widget base class that is not related to the animal hierarchy.
10.
Russell says that " A class is said to " exist " when it has at least one member . . . the class which has no members is called the " null class " . . . " ? is the null-class " is equivalent to " ? does not exist ".
