Crush Your OOPs Interview: Expert Tips and Must-Know Questions Revealed

In this post, we’ll talk about what OOPS is and answer some basic to advanced questions for both freshers and experienced professionals. This article also captures insights on Python and C# inquiries in OOPS. We’ve put together a list of the most common OOPs interview questions to help you in interviews and real-life situations.

Object-oriented programming (OOP) is an introductory programming idea, so this topic can come up in every interview you go to. To make you shine in your job interviews, we have got you covered.

Meaning of OOPS

Object-Oriented Programming, or OOP, is a type of programming in computer science based on classes and objects. Categories break up chunks of code into smaller pieces that are easier to work with and can be used to make new objects. Python, Java, C++, and JavaScript are all object-oriented programming languages that are very popular.

OOP languages can be used for more than just object-oriented programming. Programming languages like JavaScript, Python, and PHP can be used for procedure- and object-based programming.

When it comes to software development, OOPS has a lot of advantages.

OOP turns complicated systems into building blocks that can be used repeatedly.

OOP objects used more than once can be moved between applications.

Thanks to polymorphism, classes can act in different ways.

Less work is needed to fix the types because teachers already know what needs to be done.

Encapsulation is a way to keep data private.

Next, we’ll take a deeper look at OOPS interview questions and answers in the following manner 

  • Basic level questions for Freshers
  • Intermediate-level questions for Experienced Professionals 
  • OOPS interview questions in C#

OOPS Interview Questions for Freshers 

Q. What is the definition of polymorphism?

When a message can be understood in more than one way, it is said to be polymorphic. The word “polymorphism” is used to describe situations in which many different forms exist at the same time.

There are two different kinds of polymorphism.

Type in the time to finish.

 Overloading, also called polymorphism, happens when a gene is copied more than once.

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Q. In what circumstances does the Override technique function?

The override keyword lets you change a method’s execution without changing its signature.

In some cases, an instance of a derived class’s method can act as a drop-in replacement for a base class’s method.

Using “virtual/override” and similar expressions can help you do this.

Suppose you want a derived class to override a virtual method. In that case, you must add the override keyword after the virtual keyword in the documentation for the base class.

When an object from the base class is cast to the derived Class, the reference to a method from the base class is replaced with a form from the derived Class.

Q. What is the meaning of the term “constructor”?

When a new class instance is created, the Object() [native code] method is invoked.

When a new instance of a class is created, the procedure Object.setPrivateFieldValues is used to set the values of the Class’s private fields. This is known as “native code.”

If a class doesn’t have an Object() function, the compiler will make one for it automatically (in native code).

Object() [native code] defaults to setting all integer fields to zero and all string and Object fields to null.

Q. What is the meaning of encapsulation?

Encapsulation, often known as “wrapping,” is a typical hiding method and attribute technique. It encapsulates code and data, making it more challenging to determine what they are and increasing their security. Class is thus the best illustration of encapsulation.

Q.When could an Abstract Class be used?

Abstract classes should be employed when their underlying classes are assumed to implement the required metaphors by default. There is still a requirement for additional overridden methods in child classes. Abstract classes are a requirement.

OOPS Interview Questions for Experienced Professionals

Q. What are the most important differences when you compare classes and structures?

When a new instance of a class is made, its data is put on the heap by the CLR. Defining a class makes inheritance possible. Variables in classes can be given the value “null.” Procedures for building and breaking down could be part of a class. Structure, on the other hand, is a distinct type of value. Stacks are used to storing structures and can’t be passed down from generation to generation. Empty parts of a structure are not possible. Members of the structure can be set up on their own without a function called Object () or a destructor.


Q. Why is it essential to understand abstract classes? Describe the features of an abstract class.

Abstract classes are never used by themselves. Instead, they are used to build other classes.

They have the following features:

It is not possible to directly instantiate an abstract class. This means that an object of an abstract class must be passed down instead of being made from scratch.

An abstract class can have objects that are both abstract and not abstract.

At least one abstract method must be named in the abstract Class.

A private abstract class is not possible.

When the abstract keyword is used in a class declaration, the Class is said to be abstract.

The primary purpose of an abstract class is to give a shared definition of the base class that other classes can use.

Q. What is the meaning of the word “inheritance”?

Through a feature of OOPs called “inheritance,” classes can take on the traits of other courses that are used more often. Suppose there is a class called “vehicle,” for example. Different classes, called “car,” “bike,” etc., can inherit beneficial properties from it. This feature makes it possible to reduce the size of the code by getting rid of instructions that aren’t needed.

Q. What are the different ways that inheritance can be set up?

  • Single inheritance
  • Multiple inheritances
  • Multilevel inheritance
  • Hierarchical inheritance
  • Hybrid inheritance

Q. How can one define the meaning of “superclass”?

A class with an incidental relationship to one or more other classes is called a “superclass” or “base class.” The class “Car” is part of the class “Vehicle.”

Q. What are “access specifiers” in OOP?

In OOP, keywords called “access specifiers” or “access modifiers” are used to tell the program’s users which methods, classes, etc., they can see. With the help of these access specifiers, encapsulation can be set up. The most common access specifiers are public, private, and protected. Of course, there are a few more specific to each programming language.

OOPS interview questions in C#

Q. What is the use of private constructors in C#?

Until this is done, object curation for a class can be put on hold. As such, the singleton class uses it. It lets you stop a class from being passed down.

Q. What does a “destructor” do?

Destructors are used to free up any memory or resources allocated dynamically. When the Object is thrown away, it is called “right away.”

Q.Specify Namespaces.

A framework for putting the code together can be provided by permitting the system.

Q.What does “Override” mean in C#?

It adds a method, property, indexer, or event from the base class to the derived Class.

Q. Explain in words what you mean by “interface.”

An Interface exactly copies the way a class looks. There is no sample code for using the Interface, which is a shame. Interface moves around the declarations of events, indexers, and properties. 

Q.Is it possible to hand down a C# Enum?

No, you cannot inherit an Enum in C# because Enums are sealed by default.

Q.What is the definition of a constant?

The “const” keyword in C# refers to a constant. These values are visible during compilation and cannot be modified. The application is fully operational, it only changes its values while they are in use.

Q. List the various Design Patterns.

Design patterns are classified into three types:

  • Patterns for Creating New Objects and Classes are a subset of Creational Patterns.
  • Class and Object Composition are the focus of this set of structural patterns.
  • Behavior patterns It discusses the interaction between classes and objects.

Q. What are the essential parts of OOP in Python?

OOP in Python is similar to OOP in other languages. Even though the words are different, the ideas are the same. Here are some of the oldest and most essential concepts that are still used today:

  • Classes and objects
  • Inheritance
  • Encapsulation
  • Polymorphism
  • Abstraction

These are also essential parts of classic OOP. “Class” is the word that defines a class in Python. In the same way, objects are what a class looks like in the real world.In OOP, inheritance is the same thing as genetic inheritance. Classes get their properties from the classes that came before them. In Python, there are four different ways to do this:

  • Single inheritance
  • Multiple inheritances
  • Multilevel inheritance
  • Hierarchical inheritance


Before you go to the interview, you should work on solving hard coding and programming problems. Just as important as knowing the basics of Object-Oriented programming and applying OOP principles to real-world problems is being able to deal with theoretical issues. Suppose you are applying for a job as a senior developer or a programmer. In that case, you should be ready to answer questions about object-oriented programming systems (OOPS).

I hope this article helped you learn about interview questions that have to do with OOPs. It would be best to spend as much time as you can practicing and thinking about what you did in the past.

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