What does “Recursive type bound” in Generics mean?

Question

I am reading the chapter on Generics from Effective Java[Item 27].

There is this paragraph in the book:

It is permissible, though relative

Answer 1

What is recursive type bound

This: >

Note that the type parameter T is also part of the signature of the super interface Comparable.

and how does the above piece of code help achieve mutual comparability?

It ensures that you can only compare objects of type T. Without the type bound, Comparable compares any two Objects. With the type bound, the compiler can ensure that only two objects of type T are compared.