Object Oriented Programming · Complete Question Bank

All Object Oriented Programming Interview Questions

Practice the complete collection of Object Oriented Programming interview questions including theory, coding, MCQs and real interview problems.

Total Questions: 127Topics: 42Complete interview preparation

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All Object Oriented Programming Interview Questions (127)

Scroll through every important Object Oriented Programming question asked in real interviews. Includes MCQs, subjective questions, and coding prompts.

1. What does Object Oriented Programming mainly focus on?

Difficulty: EasyType: MCQTopic: OOP Basics

Using functions to perform tasks
Representing real-world entities using objects and classes
Writing code without any structure
Executing commands line by line

Object Oriented Programming models real-world entities as objects that contain both data and behavior. This makes programs modular, reusable, and easier to maintain compared to procedural approaches.

Correct Answer: Representing real-world entities using objects and classes

2. What is the relationship between a class and an object?

Difficulty: EasyType: MCQTopic: Classes Objects

A class is an instance of an object
An object is an instance of a class
They are the same thing

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All Object Oriented Programming Interview Questions

Overview

1. What does Object Oriented Programming mainly focus on?

2. What is the relationship between a class and an object?

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3. What is encapsulation in OOP?

4. Explain abstraction and how it helps in reducing program complexity.

5. Which OOP principle allows a class to use properties and behavior of another class?

6. Polymorphism in OOP allows what kind of behavior?

7. What is method overloading?

8. Which concept allows a subclass to redefine a method already defined in its superclass?

9. Describe the lifecycle of an object in OOP.

10. Which access modifier makes a member accessible only within its own class?

11. Explain the concept of composition and how it differs from inheritance.

12. Give a real-world example illustrating all four major OOP principles together.

13. Which of the following is NOT a benefit of OOP?

14. What is a class in object-oriented programming?

15. Which statement correctly creates an object from class Car in Java?

16. What does a default constructor refer to?

17. Which constructor takes arguments to initialize object at creation time?

18. What is a copy constructor used for in C++?

19. What is constructor chaining?

20. Which is true of static members versus instance members in a class?

21. What is the purpose of a destructor in C++?

22. Which operator in Java checks whether two object references point to the exact same object?

23. Explain how constructor visibility (public, private etc.) affects object creation.

24. Differentiate between default and parameterised constructors with examples.

25. Describe the lifecycle of an object from creation to destruction including constructors and destructors/garbage-collection.

26. What is the difference between shallow copy and deep copy of objects? Give examples.

27. Explain how constructor chaining works in class inheritance (base and derived classes).

28. What is single inheritance in object-oriented programming?

29. What is true about multiple inheritance (in languages that support it)?

30. In OOP, the relationship between a subclass and its superclass is often referred to as?

31. What is method overriding in OOP?

32. Which of the following is an example of compile-time polymorphism?

33. Which of these describes runtime polymorphism?

34. Given ‘Animal a = new Dog();’ which concept is illustrated?

35. One benefit of inheritance is:

36. What is the “diamond problem” in multiple inheritance?

37. Explain how inheritance and polymorphism work together in OOP.

38. Describe the types of inheritance (single, multilevel, hierarchical, multiple, hybrid) and give examples.

39. Differentiate method overloading from method overriding and discuss their use-cases.

40. What are the benefits of polymorphism in software design?

41. Why should you avoid improper inheritance and prefer composition in some cases? Provide reasons.

42. What is encapsulation in object-oriented programming?

43. What does abstraction focus on in OOP?

44. Which statement correctly distinguishes encapsulation from abstraction?

45. Which access modifier is most commonly used in encapsulation to hide a field from external access?

46. Using an interface to define common methods without implementation is an example of which OOP principle?

47. What is the main benefit of data hiding in encapsulation?

48. An abstract class cannot _____ in many OOP languages.

49. How does encapsulation support modularity in OOP?

50. What are the benefits of abstraction in object-oriented programming?

51. Describe a use-case where encapsulation improves reliability and maintainability of code.

52. Give an example code scenario illustrating both abstraction and encapsulation, and explain how they differ.

53. What are the risks or drawbacks of improper encapsulation, and how can they be mitigated?

54. What best describes an interface in object-oriented programming?

55. Which statement correctly defines an abstract class?

56. In Java, how do you use an interface and how do you use an abstract class in declaration?

57. Which is true about interfaces and abstract classes regarding multiple inheritance in Java?

58. When would you prefer using an abstract class over an interface?

59. Which feature was added in Java 8 that changed how interfaces are used?

60. Can an abstract class have a constructor and what is its purpose?

61. In Java, what are the properties of variables declared inside an interface by default?

62. Explain how interfaces provide abstraction in OOP and give an example.

63. Compare abstract classes and interfaces, and describe when you would choose one over the other.

64. Given a scenario where you need to design a plugin architecture allowing many modules, some sharing common behaviour and others not, how would you use abstract classes and interfaces?

65. What is a constructor in an object-oriented class?

66. Which type of constructor takes no parameters and is provided automatically if no constructor is defined?

67. What is the purpose of a parameterised constructor?

68. In C++, what is a copy constructor used for?

69. What is a destructor in object-oriented programming?

70. Which of the following best describes the lifetime of an object?

71. What is a memory leak in the context of objects?

72. How does garbage collection differ from deterministic destruction in object-oriented languages?

73. Explain constructor chaining and how it supports object initialization in class hierarchies.

74. Describe shallow copy versus deep copy of objects and when each should be used.

75. How are object cleanup tasks handled in Java and what are the limitations of finalisers?

76. Explain the Rule of Three (and Rule of Five) in C++ and why it matters for memory management in classes.

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