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Need Explanation for a question in Generics

thanvi janu
Greenhorn

Joined: Nov 16, 2009
Posts: 29
Hi All,



Question:


Answer was: Fails to compile.

can some one explain me the answer.


Thanks a lot,
thanvi
Rob Spoor
Sheriff

Joined: Oct 27, 2005
Posts: 19696
    
  20

Because you use a wildcard in the declaration of house, the compiler no longer knows it is a AnimalHouse<Cat>. For all it knows it could be an AnimalHouse<Dog>, AnimalHouse<Bird> or even AnimalHouse<String>*. You need to replace the "?" with either "Cat" or "? super Cat".


* Change the declaration of AnimalHouse to this:
This way the generic type is bound to be Animal or any subtype.


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