Checking if object is in array with generic method

Question

In “Java the Complete Reference” by Herbert Schildt (10th edition), in chapter 14 on Generics there is the following example of a generic method that checks if an object is in an array:

class GenMethDemo {

    static <T extends Comparable<T>, V extends T> boolean isIn(T x, V[] y) {
        . . .
    }

    . . .
}

I don’t understand why V extends T is used here.

Why do we allow array’s type to be the subclass of the object that we check for membership? Shouldn’t it be the other way around?

Answer 1

In this case V needs to be a subclass of T as you want to call Comparable methods on the V[]. If you would allow V to be a super type of T (e.g. an Object[]) you can not call compareTo as these methods are not implemented.