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Editorial Team
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Asked: 2026-05-24T05:50:00+00:00

supposed we know that ViewGroup extends View. Further we have a generic, parametrized class

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supposed we know that ViewGroup extends View.
Further we have a generic, parametrized class A<T extends View>

Question:
Why wont method C.add() accept new A<ViewGroup>() as parameter?
Shouldn’t it work, because of polymorphism?

Class diagram

SOLUTION:
Singning add with ? extends View lets add accept new A<ViewGroup>() as a parameter.

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1 Answer

  1. Editorial Team

    You signed your add method as:

    static void add(A<View>)

    but you probably meant:

    static void add(A<? extends View> a)
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