Generics wildcard parameter lower bound to Object

Question

It is possible to specify a wildcard type that has a lower bound to Object :

public void method(Collection<? super Object> c) {
    // compiles, but ? can only be Object
}

Logically the unknown type can only be Object (no type is above Object in the class hierarchy).

Is there ever a requirement or good reason to use a type of <? super Object> <? super Object> ?

Answer 1

yes, there is a use case for "? super XXXXXX", as outlines here . the gist is the using user/extends will make your collection either read only or write only.