If you consider this example:

    class Base<T> {
        T f() { return null; }
    }
    class A<T2> extends Base<T2> {
        @Override
        T2 f() { return null; }
    }
    class B extends Base<Integer> {
        @Override
        Integer f() { return null; }
    }
    class C {
        Integer f() { return null; }
    }

Base has a parameter T which is erased in Base.

A has a parameter T2 which is erased in A.

B because B is not a generic class and nothing is erased from B.

Base has the same shape as A; B has the same shape as C.