WHAT DOES ABSTRACT CLASS DIFFER FROM INTERFACE
Abstract classes and interfaces are both concepts used in object-oriented programming to define contracts and provide a level of abstraction. However, there are some key differences between them:
Definition:
Abstract Class: An abstract class is a class that cannot be instantiated and serves as a blueprint for other classes. It can contain a combination of abstract and non-abstract methods, including method implementations.
Interface: An interface is a collection of abstract methods that define a contract for classes to implement. It cannot contain method implementations or member variables.
Instantiation:
Abstract Class: You cannot create an instance of an abstract class. It is meant to be extended by subclasses that provide implementations for its abstract methods.
Interface: You cannot create an instance of an interface. Instead, classes can implement one or more interfaces, providing implementations for all the methods defined in the interface.
Inheritance:
Abstract Class: A class can inherit from only one abstract class. It supports both abstract and concrete methods, allowing for code reuse and extension of functionality.
Interface: A class can implement multiple interfaces, providing implementations for all the methods defined in each interface. Interfaces enable a class to define specific contracts it adheres to.
Method Implementation:
Abstract Class: An abstract class can contain both abstract and non-abstract methods. Non-abstract methods have a default implementation in the abstract class and can be directly used by subclasses.
Interface: Interfaces can only contain method signatures (definitions) without any method implementations. Classes that implement the interface must provide their own implementation for all methods.
Usage and Design:
Abstract Class: Abstract classes are suitable when you want to provide a common base for a group of related classes, where the abstract class provides some default behavior and subclasses provide specific implementations.
Interface: Interfaces are used when you want to define a contract or behavior that can be implemented by unrelated classes. They allow for loose coupling and flexibility in designing systems with interchangeable components.
In summary, abstract classes are used when you want to provide a common base with both abstract and concrete methods, while interfaces are used to define contracts with only method signatures. Abstract classes support inheritance and provide default method implementations, while interfaces allow multiple inheritance and enforce implementation of all methods.