The Difference Between Interface And Abstract Class: Understanding The Basics
When it comes to object-oriented programming, two concepts that often get confused are interface and abstract class. Both are essential tools for building modular and extensible code, but they have different purposes and use cases.
Understanding Interface
An interface is a collection of method signatures that defines a set of behaviors that a class must implement. In other words, it describes what an object can do, without specifying how it does it. Interfaces allow you to define a common contract that multiple classes can implement, even if they have completely different internal implementations.
For example, imagine that you are building a drawing application, and you want to define a shape interface that all your shapes must implement. The shape interface could have methods such as GetArea(), Draw(), and Move(). By defining this contract, you can write generic code that can work with any shape, without knowing anything about their implementation.
Another advantage of interfaces is that they enable polymorphism, which allows you to write code that can work with objects of different types. For instance, you could have a function that takes an IShape interface, and it would be able to accept any shape that implements the interface.
Understanding Abstract Class
An abstract class is a class that cannot be instantiated on its own, but it provides a common base for other classes to inherit from. An abstract class can contain a mix of concrete and abstract methods, where concrete methods have a defined implementation and abstract methods only have method signatures.
Abstract classes are useful when you want to define a general structure for a group of related classes, but you don’t want to provide a complete implementation for all of them. Abstract classes can have constructors, fields, and even non-abstract methods, which means they can provide partially implemented behavior to their derived classes.
For instance, you could have an abstract class called Vehicle that defines basic properties such as Make and Model, and some concrete methods such as Drive and Stop. You could then define several derived classes that inherit from Vehicle, such as Car, Truck, and Motorcycle, which can provide their own implementation of the abstract methods.
Differences Between Interface And Abstract Class
Now that we’ve covered the basics of both interface and abstract class, let’s highlight some of the key differences between them:
– A class can implement multiple interfaces, but it can only inherit from one abstract class.
– All methods in an interface are abstract, but an abstract class can have both abstract and non-abstract methods.
– Interfaces cannot have fields, constructors, or non-public methods, while abstract classes can have all of these.
– Interfaces are used to define a contract for a group of related classes, while abstract classes are used to provide common behavior and structure for a group of related classes.
In conclusion, both interface and abstract class are powerful tools for building modular and extensible code. Interfaces are useful when you want to define a contract for a group of related classes, while abstract classes are useful when you want to provide partially implemented behavior and structure to a group of related classes. By understanding the differences between these two concepts, you can choose the most appropriate tool for your specific needs.
Table difference between interface and abstract class
| Interface | Abstract Class |
|---|---|
| An interface is a collection of abstract methods and constants that can be used to define a contract between a class and the outside world. | An abstract class is a class that cannot be instantiated and is used as a base class for other classes to inherit from. |
| Interfaces provide full abstraction and only the signature of the methods is exposed to the outside world. | Abstract classes can provide both concrete and abstract methods and are used when we want to provide some default implementations or common behavior to the classes that will inherit from it. |
| Multiple interfaces can be implemented by a single class. | A class can inherit from only one abstract class. |
| An interface is used when we want to achieve complete abstraction and provide only the necessary details required by the client classes. | An abstract class is used when we want to provide some default implementations and common behavior to the classes that will inherit from it. |