10 Differences Between class and interface

Difference between Class and Interface

What is a Class?

A class is a blueprint for creating objects (a particular data structure), providing initial values for state (member variables or attributes), and implementations of behavior (member functions or methods).

Examples of Class:

Here are a few examples of classes:

  • Person
  • Car
  • Rectangle

Uses of Class:

Classes are extensively used in object-oriented programming to create objects that have similar characteristics and functionalities. They allow us to create complex systems by organizing code into manageable and reusable components.

What is an Interface?

An interface is a collection of abstract methods (methods without a body) that defines a contract for what a class implementing the interface should do. It specifies the methods that a class must implement.

Examples of Interface:

Here are a few examples of interfaces:

  • Comparable
  • Serializable
  • Iterator

Uses of Interface:

Interfaces are used to define common behavior that multiple classes can implement. They promote code reusability and allow flexibility in adding behavior to different classes without having to change the class itself.

Differences between Class and Interface:

Difference Area Class Interface
Definition A class is a blueprint for creating objects. An interface is a collection of abstract methods.
Inheritance Classes support both single and multiple inheritance. Interfaces support multiple inheritance.
Implementation Classes can provide implementations for methods. Interfaces cannot provide implementations, only method signatures.
Object Creation Objects can be created from classes using the “new” keyword. Interfaces cannot be instantiated; they are implemented by classes.
Accessibility Classes can have different access specifiers (public, private, protected). Interface members are implicitly public and cannot have access specifiers.
Variables Classes can have member variables. Interfaces cannot have member variables (only constants).
Constructor Classes can have constructors for object initialization. Interfaces cannot have constructors.
Extending Classes can extend other classes. Interfaces cannot extend classes, but they can extend other interfaces.
Type of Relationship Class relationship represents “is-a” or inheritance relationship. Interface relationship represents “has-a” or capability relationship.
Implementation Limit A class can only extend one class (single inheritance). A class can implement multiple interfaces (multiple inheritance).


In summary, classes and interfaces are fundamental concepts in object-oriented programming. Classes are blueprints for creating objects with state and behavior, while interfaces define a contract for what a class must do without providing any implementation details. Classes support inheritance, can have member variables, implement constructors, and more. On the other hand, interfaces allow multiple inheritance, have no member variables, and cannot be instantiated.

People Also Ask:

1. Can a class implement multiple interfaces?

Yes, a class can implement multiple interfaces. This is one of the key differences between classes and interfaces.

2. Can interfaces have variables?

No, interfaces cannot have member variables. They can only have constants.

3. Do interfaces provide method implementations?

No, interfaces solely provide method signatures without any implementation details. It is the responsibility of the implementing class to provide the method implementations.

4. Can an interface extend a class?

No, interfaces cannot extend classes, but they can extend other interfaces. Inheritance is only possible between classes.

5. What is the purpose of multiple inheritance in interfaces?

Multiple inheritance in interfaces allows a class to inherit behavior from multiple sources, enabling greater flexibility and code reuse.

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