Object-Oriented Programming (OOP or OOPS) is a fundamental concept that every software developer and engineer must master. Whether you are a fresher or an experienced professional, knowing the top 50 OOPS interview questions can be the game-changer for your next interview.
This article provides a comprehensive list of OOPS interview questions and answers, making your preparation easy and structured.
People Also Ask
What are the 4 basics of OOP?
The four basics of OOP are Encapsulation, Inheritance, Polymorphism, and Abstraction.
What are the 5 basic concepts of OOP?
The five basic concepts are Class, Object, Encapsulation, Inheritance, and Polymorphism.
What are the 4 types in OOPs?
The four pillars (types) in OOPS are Encapsulation, Inheritance, Polymorphism, and Abstraction.
Top 50 OOPS Interview Questions
1. What is Object-Oriented Programming (OOPS)?
Answer:
OOPS is a programming paradigm centered around objects rather than actions. It structures software into simple, reusable pieces of code.
2. What are the main principles of OOPS?
Answer:
Encapsulation, Inheritance, Polymorphism, and Abstraction.
3. What is a Class?
Answer:
A class is a blueprint for creating objects. It defines attributes and methods.
4. What is an Object?
Answer:
An object is an instance of a class containing data and behavior.
5. What is Encapsulation?
Answer:
Encapsulation binds data and methods together and restricts direct access to some components.
6. What is Inheritance?
Answer:
Inheritance allows a class to inherit properties and behavior from another class.
7. What is Polymorphism?
Answer:
Polymorphism allows methods to behave differently based on the object calling them.
8. What is Abstraction?
Answer:
Abstraction hides unnecessary details and shows only essential features.
9. What is a Constructor?
Answer:
A constructor is a special method invoked when an object is created.
10. What is a Destructor?
Answer:
A destructor is a method that is automatically invoked when an object is destroyed.
11. What is Method Overloading?
Answer:
Defining multiple methods with the same name but different parameters.
12. What is Method Overriding?
Answer:
Replacing a base class method in a derived class with a new version.
13. What is Multiple Inheritance?
Answer:
A class inherits from more than one base class.
14. What is Multilevel Inheritance?
Answer:
A class inherits from a derived class, forming a hierarchy.
15. What is Hybrid Inheritance?
Answer:
A combination of multiple types of inheritance.
16. What is an Interface?
Answer:
An interface is a contract that defines a set of methods without implementation.
17. What is an Abstract Class?
Answer:
An abstract class contains abstract methods that must be implemented in derived classes.
18. What is the difference between Abstract Class and Interface?
Answer:
Abstract classes can have method implementations, while interfaces cannot (in many languages).
19. What is a Static Variable?
Answer:
A variable associated with a class, not instances.
20. What is a Final Class?
Answer:
A final class cannot be extended/inherited.
21. Explain Association in OOPS.
Answer:
Association represents a relationship between two classes.
22. What is Aggregation?
Answer:
Aggregation is a special form of Association where one class owns another.
23. What is Composition?
Answer:
Composition is a strong type of Aggregation where child objects cannot exist independently.
24. What is the difference between Aggregation and Composition?
Answer:
In Composition, the lifetime of the owned object depends on the owner.
25. What is a Copy Constructor?
Answer:
A constructor that initializes a new object using an existing object.
26. What is Dynamic Binding?
Answer:
Dynamic binding happens when a method call is resolved at runtime.
27. What is Static Binding?
Answer:
Static binding happens when a method call is resolved at compile-time.
28. What is an Access Modifier?
Answer:
Access Modifiers like public, private, and protected control the visibility of class members.
29. What is the role of the ‘this’ keyword?
Answer:
‘this’ refers to the current object.
30. What is a Virtual Function?
Answer:
A function that can be overridden in a derived class.
31. What is an Inline Function?
Answer:
An inline function suggests the compiler insert the function code directly into the calling code.
32. What is Friend Function?
Answer:
A friend function can access private and protected members of a class.
33. What is a Pure Virtual Function?
Answer:
A function with no implementation in the base class, meant to be overridden.
34. What is Operator Overloading?
Answer:
Redefining the meaning of an operator for user-defined types.
35. Explain Early and Late Binding.
Answer:
- Early Binding: Compile-time decision.
- Late Binding: Run-time decision.
36. What is Data Hiding?
Answer:
Restricting access to internal object details to ensure controlled interaction.
37. What is Cohesion?
Answer:
Cohesion refers to how closely related and focused the responsibilities of a single module are.
38. What is Coupling?
Answer:
Coupling measures how much one class is dependent on another.
39. What is a Template?
Answer:
Templates allow functions and classes to operate with generic types.
40. What is Exception Handling?
Answer:
Exception Handling manages runtime errors gracefully using constructs like try, catch, and finally.
41. What is RTTI (Run Time Type Identification)?
Answer:
RTTI lets you find the type of an object at runtime.
42. What is a Smart Pointer?
Answer:
A smart pointer is an object that acts like a pointer but provides automatic memory management.
43. What is Serialization?
Answer:
Serialization converts an object into a byte stream for storage or transmission.
44. What is Deserialization?
Answer:
Deserialization is the process of converting a byte stream back to an object.
45. What is a Singleton Class?
Answer:
A Singleton class allows only one instance of itself to be created.
46. What is the importance of OOPS?
Answer:
OOPS improves code reusability, scalability, and maintainability.
47. What is Data Abstraction?
Answer:
Data Abstraction provides only essential information to the user and hides internal details.
48. What is UML?
Answer:
Unified Modeling Language (UML) is used to model software architecture visually.
49. What is MVC Architecture?
Answer:
Model-View-Controller (MVC) is a design pattern that separates an application into three interconnected components.
50. What are SOLID Principles in OOPS?
Answer:
SOLID is an acronym for five design principles: Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, Dependency Inversion.
Conclusion
Mastering these 50 OOPS interview questions can boost your confidence and increase your chances of success in technical interviews. Focus on understanding the concepts deeply, practice real-world coding problems, and you’ll be well-prepared to showcase your skills.
Good luck with your next interview!