interface and abstract class

Lalit Raghav

10y2.1kVisual Basic .NET

difference between interface and abstract class with only abstract method.

Please give me explanation not link

3 Replies

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Amit Choudhary10y ago
The differences between Interfaces and Abstract classes can be categorized by concept and implementation.

From Object oriented view
As you might be knowing the basic principles of object oriented language.
- Abstraction/Encapsulation
- Inheritance
- Polymorphism

Interface
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Interfaces provides high level of abstraction.
They also known as contracts in some design principles of software system.
Decoupled system uses Interfaces to expose dependencies because they represent declarations and not actual implementations. Because Interfaces abstracts implementation besides interface can have multiple definitions represented by multiple classes those implements those interfaces. So they are important part of a software system design which is(should be) less coupled and more cohesive.

Abstract class
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Abstract classes represents a level of abstraction and high level of information sharing also known as Inheritance. Interfaces are not for data sharing at all.
Abstract classes are to define default behavior of any entity(class). It also allows to define abstract and virtual actions. Those actions represents derived/child class implementation. So polymorphism comes in picture. Which interfaces doesn't represent in any way.
When you being learning object oriented system or language its remains confusing in beginning but when you spent years practicing and learning the same, you realize that there's not much to compare for differences because these two things exists for their own purpose.

Difference from C# perspective
C# is a language which follows Object oriented principles. C# doesn't support multiple inheritance which make it close to pure object oriented language. Since C++ has this feature and we learn C++ as first class language during our college time so we compare features. Then question comes how the multiple inheritance works in C#. From many source you learn that there's interface that allows something like multiple inheritance but here the wrong information start crawling into mind and people starts comparing Abstract classes and Interfaces. Interface doesn't have Information sharing i.e. Inheritance feature. They're contracts which declares rules/actions which any class should implement in order to fulfill the contract rules(explained in simple words).

What are difference in these two terms in C#?
You can follow other answers to get the details about the differences. :)

The difference is by concept of OOP and not just in C#. So my above answer applied to any language which follows OOP and not just C#.

I think I can post this answer as blog too. Cheers!!

Krishna Rajput Singh10y ago

Hello Lalit Raghav thanks for writing belo answer and links i hope helpful for you ...:)

http://beginnersbook.com/2013/05/abstract-class-vs-interface-in-java/

http://www.codeproject.com/Articles/11155/Abstract-Class-versus-Interface

Feature	Interface	Abstract class
Multiple inheritance	A class may inherit several interfaces.	A class may inherit only one abstract class.
Default implementation	An interface cannot provide any code, just the signature.	An abstract class can provide complete, default code and/or just the details that have to be overridden.
Access Modfiers	An interface cannot have access modifiers for the subs, functions, properties etc everything is assumed as public	An abstract class can contain access modifiers for the subs, functions, properties
Core VS Peripheral	Interfaces are used to define the peripheral abilities of a class. In other words both Human and Vehicle can inherit from a IMovable interface.	An abstract class defines the core identity of a class and there it is used for objects of the same type.
Homogeneity	If various implementations only share method signatures then it is better to use Interfaces.	If various implementations are of the same kind and use common behaviour or status then abstract class is better to use.
Speed	Requires more time to find the actual method in the corresponding classes.	Fast
Adding functionality (Versioning)	If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method.	If we add a new method to an abstract class then we have the option of providing default implementation and therefore all the existing code might work properly.
Fields and Constants	No fields can be defined in interfaces	An abstract class can have fields and constrants defined

if answer helpful mark as correct

Praveen Dhatrika10y ago
One main difference between Interface and Abstract class is that, Both have incomplete methods (declarations but no definition), but an interface can have only methods declaration and definition outside when inherited, where as an abstract class is similar like interface calls but it also has fields (properties)in them, as it's a class.

And AbstractClass will have AbstractMethods which have kinda same functionality as interfaces, but again you can your definition with in the same class.

One can't serve all the food you like, in one plate, you need to help your self.

please help your self in, going through the links

http://csharp-video-tutorials.blogspot.com/2012/06/part-33-c-tutorial-difference-between.html
http://www.c-sharpcorner.com/Forums/Search/?searchtext=abstract-classes-and-interfaces