I have two examples of methods that uses wildcard generics.
First example:
public static <T extends Comparable> T findMax(List<T> list)
Second example:
public static <T extends Comparable<? super T>> T findMax(List<? extends T> list)
I want to know if these two examples are redundant. If yes, why?
The two examples are telling you different things, so they are not redundant, they give different information and restricts the type in a different way.
public static <T extends Comparable> T findMax(List<T> list)
In this example, you are telling your T variable can be of any type that implements or extends Comparable (if it is a class or an interface)
public static <T extends Comparable<? super T>> T findMax(List<? extends T> list)
In this example, you are telling that the T type should extends comparable and also telling that the type must be a super class of T (inside comparable) but it can be a sub-type of T in the list.
Both wildcards make a difference.
The first one says that T or a supertype of T must implement the Comparable interface. The second one says that you can use a List of objects of type T or of subtype of T.
