0

In the question,I learned that the polymorphism has 4 types:

  1. Coercion,

  2. Overloading

  3. Parametric Polymorphism

  4. Inclusion

    So I did not completely understand what does mean by Inclusion, I need same example to implement this notion.

Community
  • 1
  • 1
moradov
  • 109
  • 3

2 Answers2

0

As already suggested, search a little bit yourself to get a deeper idea of this topic... Here is one possible explanation:

[...] subtyping allows a function to be written to take an object of a certain type T, but also work correctly, if passed an object that belongs to a type S that is a subtype of T (according to the Liskov substitution principle) Wikipedia - Polymorphism

abstract class Vehicle
{
    abstract void move();
}

class Car extends Vehicle
{
    public void move() { ... }
}

class Ship extends Vehicle
{
    public void move() { ... }
}

public void moveVehicle(Vehicle v)
{
    v.move();
}

Here is an example for inclusion polymorphism:

Vehicle [] vs = new Vehicle [2];

vs[0] = new Car();
vs[1] = new Ship();

for(Vehicle v : vs)
{
    moveVehicle(v);
}

Or another example:

Car c = new Car();
Ship s = new Ship();

moveVehicle(c);
moveVehicle(s);

For additional information see the Wikipedia - Polymorphism page... But still search yourself for this topic to get a deeper idea of it!

0x1C1B
  • 1,204
  • 11
  • 40
  • i use it lot off, without i know that is exactly, the inclusion polymorphism notion, thank you very much. – moradov May 23 '18 at 15:54
0

The inclusion polymorphism means that you can instantiate an object from his super class. For example you have 

public class Person {
.
.
}

public class Employee extends Person{
.
.
}

So you can create an object 

Person x = new Employee();

This is useful for example if you need to create a lot of different object that refere to a single superType

For example you have SuperTyper geometric_figure and SubTyper figure (circle, square, triangule,..). The geometric_figure may have two attributes x,y for the screen location and an abstract method "draw",to draw on screen, that each figure ,that extend it , need to implement

Thanks to dynamic link of java when you call geometricFigure.draw(), it will automatically know what type of geometric_figure you are calling (circle, square, triangule,..), and invoce this draw method

To manually check what is his specific class you can do:

Geometric Figure x = new Square();
if(x instance of Square){...}

A popular case is when you want to refere to a generic object like this

Object x = new AnyClass();

because the Object is the generic super class that every class have. (When you do not extend anythig, by default it extand Object)

Vito Ferrulli
  • 201
  • 3
  • 10