Note:
Most of the interview persons ask What is the Use Of Abstract Class and
Interface.
Few people
may go indepth and ask you that can we do with the same with Class and what is
the use of Abstract Class and Interface.
So with
this article I am going to explain , what will happened exactly if we use Class
and when to use interface and Abstract
Abstract Class An abstract class is a special class that
contains both abstract and non-abstract members in it.
Abstract
Method
A method without any particular body is known as an abstract
method. These methods contain only declaration of the method.To declare an
abstract method, we have to use abstract modifier on the method. The
implementation of abstract method is done by a derived class. When the abstract
class inherits the derived class, the derived class must implement the abstract
methods using override keyword in it.
namespace ConsoleApplication2
{
public abstract class
Bikes
{
//Abstract
Methods
public abstract double priceOfTheBike();
public abstract int
getTotalSeatCount();
}
}
Now, I
have class like Shine and Unicorn
which are derived from a parent class called Bike. Here, I have the Bike
methods as follow:
public class Bike
{
public string Wheel()
{
return "2 wheeler";
}
public string Disc()
{
return "Disc Facility
Available";
}
public string FiveGearSystem()
{
return "Five Gear System";
}
}
public class Shine : Bike
{
static void
Main(string[] args)
{
Shine objShine = new Shine();
Console.WriteLine(objShine.Desc());
Console.WriteLine(objShine.Wheel());
Console.WriteLine(objShine.FiveGearSystem());
Console.ReadLine();
}
}
Now I am going to Add one
more class Unicorn inheriting Bike Class
public class
Unicorn : Bike
{
static void
Main(string[] args)
{
Unicorn objUnicorn = new Unicorn();
Console.WriteLine(objUnicorn.Desc());
Console.WriteLine(objUnicorn.Wheel());
Console.WriteLine(objUnicorn.FiveGearSystem());
Console.ReadLine();
}
}
If we
are taking class, then we can only write normal methods having common
implementation (i.e I mean Bike Class )there. But, this will not satisfy our
requirement because we need separate implementations in both the classes(Shine
and Unicorn Classes). Thus, we will go forward by using Class and Interface
Now what we will do is have common methods in the
Interface and Inherits that interface as shown below. So to achieve with class
Now, let me first inherit the Unicorn class from Bike class and IExtra
interface class to achieve our goal.
The code is given below.
The code is given below.
Example and Output:
namespace ConsoleApplication2
{
public interface IExtra
{
double price();
string colors();
}
public class
Bike
{
public string Wheel()
{
return "2 wheeler";
}
public string Desc()
{
return "Desc Facility
Available";
}
public string FiveGearSystem()
{
return "Five Gear System";
}
}
public class
Unicorn : Bike,IExtra
{
public string DiscountPrice()
{
return "20% discount on buying
Unicorn Bike";
}
static void
Main(string[] args)
{
Unicorn objUnicorn = new Unicorn();
Console.WriteLine("Below are the
Common properties defined in the Bike Class");
Console.WriteLine(objUnicorn.Desc());
Console.WriteLine(objUnicorn.Wheel());
Console.WriteLine(objUnicorn.FiveGearSystem());
Console.WriteLine("Below are the
Common methods but implementation is Different");
Console.WriteLine("Total ONRoad
Price:" + objUnicorn.price());
Console.WriteLine(objUnicorn.colors());
Console.WriteLine("Below is the Own
Method defined in the Unicorn Class");
Console.WriteLine(objUnicorn.DiscountPrice());
Console.ReadLine();
}
public string colors()
{
return "Black with Gray
Strips";
}
public double price()
{
return 60000;
}
}
}
Output:
Picotrial Way:
Note: Now you can answer, the interview question if any one ask , you why cant we do with Classes.
Example :
public class Bike
{
public string Wheel()
{
return "2 wheeler";
}
public string PetrolVehicle()
{
return "This is Petrol Vehicle";
}
}
public class Unicorn : Bike
{
public string DiscountPrice()
{
return "20% discount on buying Unicorn Bike";
}
static void Main(string[] args)
{
Unicorn objUnicorn = new Unicorn();
Console.WriteLine(objUnicorn.PetrolVehicle());
Console.WriteLine(objUnicorn.Wheel());
Console.WriteLine(objUnicorn.DiscountPrice());
Console.ReadLine();
}
}
Example :
public class Bike
{
public string Wheel()
{
return "2 wheeler";
}
public string PetrolVehicle()
{
return "This is Petrol Vehicle";
}
}
public class Unicorn : Bike
{
public string DiscountPrice()
{
return "20% discount on buying Unicorn Bike";
}
static void Main(string[] args)
{
Unicorn objUnicorn = new Unicorn();
Console.WriteLine(objUnicorn.PetrolVehicle());
Console.WriteLine(objUnicorn.Wheel());
Console.WriteLine(objUnicorn.DiscountPrice());
Console.ReadLine();
}
}
Here we know only the Unicorn class, its methods, and properties. The user can access the Bike class property and method by creating the object of Unicorn class because it is a child class.
Now, the main drawback of this kind of Implementation is that it allows the user to create the object of the Parent class (which the user should not be aware of and this is not his strategy). Let's see what happens when the user creates the object.
From the above example it is very clear that we are not able to create the access the child method.
Now
this is very simple to solve with Abstract Class, Now we will see how to solve
this with Abstract Class, even if the user will create an object of Parent class, we need to check them because using that object, he can't able to access the child class method.
So, the main problem we face here is,
As the user is unaware of parent class, he is able to create the object of parent class and unable to access the child class method using parent class. So, to restrict this, we have to do the following things-
We should not give the permission to create the object of parent class in child class
We can only allow the user to create the child class object to access both parent class methods and child class methods.
Simple to do this
Now i am going to create a Abstract Class, and when i am going to create a Object of Abstract Class, i will get an Error as Shown Below
Second Example
Now i am going to create a Abstract Class, and when i am going to create a Object of Abstract Class, i will get an Error as Shown Below
Second Example
Create
a Abstract Class as Bike.
Add all the common functionality in simple methods and all the methods whose implementation is different but name is same. Make them Abstract method.
Add all the common functionality in simple methods and all the methods whose implementation is different but name is same. Make them Abstract method.
Example and output:
namespace ConsoleApplication2
{
public abstract class
Bike
{
//put
all the common functions but different implementation in abstract method.
public abstract double price();
public abstract string colors();
public string Wheel()
{
return "2 wheeler";
}
public string Desc()
{
return "Desc Facility
Available";
}
public string FiveGearSystem()
{
return "Five Gear System";
}
}
public class
Unicorn : Bike
{
public string DiscountPrice()
{
return "20% discount on buying
Unicorn Bike";
}
static void
Main(string[] args)
{
Unicorn objUnicorn = new Unicorn();
Console.WriteLine("Below are the
Common properties defined in the Bike Class");
Console.WriteLine(objUnicorn.Desc());
Console.WriteLine(objUnicorn.Wheel());
Console.WriteLine(objUnicorn.FiveGearSystem());
Console.WriteLine("Below are the
Common methods but implementation is Different");
Console.WriteLine("Total ONRoad
Price:" + objUnicorn.price());
Console.WriteLine(objUnicorn.colors());
Console.WriteLine("Below is the Own
Method defined in the Unicorn Class");
Console.WriteLine(objUnicorn.DiscountPrice());
Console.ReadLine();
}
public override string colors()
{
return "Black with Gray
Strips";
}
public override double price()
{
return 60000;
}
}
}
Output :
Finally the Result is
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