Generics ? super Doubt

[aslika bahini]

Hi There,

I have a doubt in the following code:
The class hierarchy is
Species
^
Animals
^
Dog

 List<?super Animals>dList =new ArrayList<Species>(); #1
   dList.add(new Dog()); #2   

I feel that Dog is not a super of Animals. But, there is no error for the line #2 in adding. for the above syntax I thought I can add only "Animals","Species","Object" in the dList. But, I am getting an compiler error saying "cannot instantiate the type".
Can any of you please explain?



Thanks in Advance
Saritha

[ October 06, 2008: Message edited by: saritha babu ]
[ October 06, 2008: Message edited by: saritha babu ]

[Rekha Srinath]

Saritha,

The how's and why's of your question is discussed here:

https://coderanch.com/t/270553/java-programmer-SCJP/certification/Generics-please-clarify

[Bob Ruth]

List<? super Animals> dlist

declares a reference variable that can hold a List of any type that is Animal OR a superclass to Animal. So your statement is correct that this could be a List<Animal>, List<Species>, or a List<Object>. When it comes to adding, since the generic type of list will hold Animal or higher, the compiler knows that it will hold anything Animal or a subclass of Animal.
You may add Dog, you may add Animal, you may not add Species, you may not add Object. The only things that you can add to a <? super ClassName> are ClassName or subclass of ClassName.

[aslika bahini]

Hi Bob,

Thanks much Bob for clarifying.

Thanks again
Saritha

[Bob Ruth]

My pleasure!