Class definition class name <>

Question

What's the sense of this class definition, what's kind of class is that?

class Node<K extends Comparable<? super K>,V>

Answer 1

This is a generic class definition. It translates to:

• class Node takes two types as parameters: K and V.
• the type K must extend the class Comparable
• the class Comparable itself, in this case, takes some type as parameter, let's call it T.
• type T must be a superclass of K.

Edit: Ok, since an example was requested, a simple instantiation of this class could be:

Node<Integer, String> node = new Node<Integer, String>();

Since the Integer class implements Comparable<Integer> it fits the above description nicely (note that super also allows type T to the the same type as K).

V has no constraints, so it can be any type.

Answer 2

It's a generic class of types K and V, where K is a type that extends Comparable of any class that is a superclass of K.

Answer 3

Looks like it's from an implementation of a red-black tree designed for explanatory purposes:

Red-black tree implemented in Java

Beyond that, it's a class called Node that takes parameters K and V, where K extends Comparable, which takes a parameter that is itself a superclass of K.