Top 10 Inheritance Interview Questions in OOP with Answers

Inheritance is one of the key concepts in object-oriented programming (OOP) and a popular topic for OOPs interviews Let’s look at the top 10 inheritance interview questions and their answers

1. What is inheritance in OOP?

Inheritance allows a new class to be defined as an extension of an existing class. The new class inherits the members of the base class. The inherited members can be used as is, replaced with new definitions, or even undefined. This promotes code reuse.

2. Why is inheritance used in OOP?

The main purposes of inheritance are

• Code Reusability – Inheritance enables the reuse of code without having to rewrite it. The existing class serves as the base.

• Extending Functionalities – We can extend the features and functionalities of a class by deriving a new class from it.

• Data Hiding – Derived classes can hide the implementation details of the members of the base class.

• Polymorphism – With inheritance, we can override base class methods in derived classes. This enables polymorphism.

3. What are the different types of inheritance?

There are 5 main types of inheritance:

• Single inheritance – One base class, one derived class
• Multiple inheritance – One derived class, multiple base classes
• Multilevel inheritance – Base class, derived class, derived from that derived class
• Hierarchical inheritance – One base class, multiple derived classes
• Hybrid inheritance – Mix of multiple inheritance types

4. What is single inheritance?

When a derived class inherits from just one base class, it is called single inheritance. One class extends the features of just one parent class.

Class A {   //members}Class B extends A {   //members} 

5. What is multiple inheritance?

When a derived class inherits from multiple base classes, it is multiple inheritance. The derived class can reuse code from multiple parent classes.

Class A {  //members}Class B { //members}Class C extends A, B {  //members}

6. Does Java support multiple inheritance?

No, Java does not support multiple inheritance with classes. A class can extend only one parent class in Java. However, it supports multiple inheritance of interfaces with interfaces extending multiple interfaces.

7. What is multilevel inheritance?

When a derived class is inherited from another derived class, it becomes multilevel inheritance. It allows for more than two levels of inheritance.

Class A {  //members }Class B extends A {  //members}Class C extends B {  //members} 

Here, Class C inherits from Class B which again inherits from Class A.

8. What is hierarchical inheritance?

When multiple derived classes inherit from the same base class, it is hierarchical inheritance. One parent class has multiple child classes inheriting from it.

Class A {  //members}Class B extends A {  //members}Class C extends A {  //members}

Here, Class B and Class C both inherit from Class A.

9. How is inheritance implemented in Python?

In Python, inheritance works implicitly. We just have to derive a child class from the parent class.

class Parent:         # members  class Child(Parent):  # members

The child class will inherit all members of the parent class.

10. How is inheritance implemented in C++ and Java?

In C++ and Java, inheritance must be explicitly specified using the ‘:’ and ‘extends’ keywords respectively.

// C++class Parent {  //members};class Child : public Parent {  //members  };// Javaclass Parent {  //members }class Child extends Parent {  //members}

The child classes derive from the parent classes explicitly.

11. What is method overriding in inheritance?

Method overriding is replacing a method of the base class with a new definition in the derived class. The base method gets overridden by the derived class method.

12. Can private members be inherited?

No, private members of a class are not inherited and remain private to that class only. The derived classes cannot directly access them.

13. Are constructors and destructors inherited?

No, constructors and destructors are not inherited. A derived class has its own constructors and destructors.

14. What is inheritance ambiguity?

When a derived class inherits two base classes with member functions of the same name, trying to access that function becomes ambiguous. The compiler cannot resolve which base class function to access.

15. How is inheritance ambiguity resolved?

Inheritance ambiguity is resolved in multiple ways:

• Renaming the method names in either base class
• Qualifying the method name with base class name
• Overriding the method in derived class

16. What are the advantages of inheritance?

Advantages of using inheritance:

• Code Reuse – Existing code can be reused in derived classes
• Extending Features – Derived classes can extend features of base classes
• Data Hiding – Implementation details can be hidden from client programs
• Polymorphism – Base class pointers can invoke derived class methods

17. What are the disadvantages of inheritance?

Some disadvantages of inheritance are:

• Tight Coupling – Changes in parent class may affect child classes
• Dependency Issues – Child classes depend heavily on parent classes
• Multiple Inheritance Issues – Inheritance ambiguity, complex hierarchies
• Testing and Debugging – Bugs can be harder to detect and fix

18. How does inheritance support polymorphism?

Inheritance enables polymorphism as derived classes can override base class methods with their own implementation. The appropriate overridden method is called based on the object at runtime.

19. How does inheritance break encapsulation?

Though inheritance promotes code reuse through inherited class members, it also breaks encapsulation by exposing the base class implementation details. Child classes rely heavily on parent class implementations.

20. When should inheritance not be used?

Inheritance should be avoided when:

• There is no “is-a” relationship between classes
• You need to reuse only some methods, not full abstraction
• The classes are tightly coupled and high dependency
• There are multiple inheritance ambiguities

Instead, composition can be used in these cases.

So these are the top 20 inheritance interview questions for OOPs interviews. Inheritance is a key concept in object-oriented programming languages like Java, Python, C++ etc. Preparing these questions will help you tackle inheritance specific questions confidently in interviews.