Default value for "interface" property

[pm771]

In my Flex 3 book I came across the following line of code:

public var dp:ICollectionView=null;

Authors have the following comment:
A value of null is used to act as the initial state of the property until a value is passed in

I was under impression that all reference-type variables are null by default. Am I mising something?

TIA, Eugene

[senocular]

they're just being explicit. If it wasn't included, it would still be null.

[pm771]

Thank you very much for the clarification.