redundant declaration of methods

Question

I want to know if there are any logical differences in declaration of these two methods:

exemple 1

public static <T extends Comparable<? super T>> T findMax(List<? extends T> list)

exemple 2

public static <T extends Comparable<? super T>> T findMax(List<T> list)

Someone told me that this part <? extends T>is equivalent with <T> and the wildcard is redundant in first exemple, and he suggested me to use the code from the second exemple. Is that right?

Answer 1

They are not the same.

Show this "someone" this counterproof :)

class Scratch
{
    interface A extends Comparable<A> {}
    interface B extends A {}

    public static <T extends Comparable<? super T>> T findMax(List<? extends T> list)
    {
        return null;
    }

    public static <T extends Comparable<? super T>> T findMax2(List<T> list)
    {
        return null;
    }

    public static void main(String[] args)
    {
        List<B> listOfBs = new ArrayList<>();

        A foo = Scratch.<A>findMax(listOfBs);  // fine
        A bar = Scratch.<A>findMax2(listOfBs); // compiler error
    }
}