Difference between Class and interface

<<–2/”>a href=”https://exam.pscnotes.com/5653-2/”>p>world of classes and interfaces in object-oriented programming (OOP).

Introduction

In the realm of object-oriented programming (OOP), classes and interfaces serve as the fundamental building blocks for structuring code, defining object blueprints, and establishing relationships between them. While both contribute to the organization and functionality of your programs, they have distinct roles and characteristics.

Key Differences Between Class and Interface (Table Format)

Feature	Class	Interface
Definition	A blueprint for creating objects, defining their properties (data) and behaviors (methods).	A contract that specifies a set of methods that a class must implement.
Instantiation	Can be instantiated to create objects.	Cannot be instantiated directly.
Inheritance	Supports single inheritance (extends one class).	Supports multiple inheritance (extends multiple interfaces).
Implementation	Provides complete implementation for its methods.	Only declares method signatures; implementation is provided by the implementing class.
Member Visibility	Members can have various access modifiers (public, private, protected).	All members are implicitly public.
Purpose	Describes the state and behavior of an object.	Defines a set of behaviors that a class must adhere to.
Use Cases	Used to model real-world entities and their interactions.	Used to achieve abstraction, polymorphism, and loose coupling.

Advantages and Disadvantages

Class

• Advantages:
  • Encapsulation of data and behavior.
  • Code reusability through inheritance.
  • Supports polymorphism for flexible object interactions.
• Disadvantages:
  • Limited to single inheritance, which can sometimes be restrictive.
  • Tight coupling between classes when using inheritance.

Interface

• Advantages:
  • Promotes abstraction by focusing on “what” an object can do, not “how.”
  • Allows for multiple inheritance, providing flexibility in design.
  • Enables loose coupling between components.
• Disadvantages:
  • Cannot be instantiated directly.
  • Requires implementing classes to provide the actual method implementations.

Similarities

• Both are reference types.
• Both can define methods.
• Both contribute to the structure and organization of OOP code.

FAQs on Class and Interface

1. Can an interface have variables?
   Yes, interfaces can have variables, but they are implicitly public, static, and final (constants).

2. Can a class implement multiple interfaces?
   Yes, a class can implement multiple interfaces, achieving a form of multiple inheritance.

3. What’s the difference between abstract classes and interfaces?
   Abstract classes can provide default implementations for some methods, while interfaces only define method signatures. Abstract classes can also have state (instance variables).

4. When should I use an interface instead of a class?
   Use an interface when you want to define a contract for behavior without providing a specific implementation. Use a class when you need to create objects with state and behavior.

5. Can an interface extend another interface?
   Yes, an interface can extend one or more other interfaces, inheriting their method signatures.

Let me know if you’d like more details or examples on any specific aspect!