Most Popular OOPs Interview Questions And Answers

Knowledge of Object Oriented Programming languages such as Java, C++, and Python is one of the most valued skills an organization demands. Multiple ways are there for candidates to widen their OOPs knowledge and ace the OOPs interview questions.

To begin with, Object Oriented Programming system deals with implementing a programming language model around an object rather than logic or procedural programming. OOP is modeled around objects that interact with one another.

We have jotted down the ideal answers to the top OOPs questions in this article which are the most asked OOPs interview questions. 

List of Top OOPs Interview Questions And Answers In 2024

Having a thorough read on the sample OOPs interview questions and answers; pretty much caters an idea of questions to expect.

The comprehensive segment includes the OOPs interview questions and answers that will boost your preparation for the next Object Oriented Programming interview questions.

If you worry about; how to prepare OOPs viva questions! Here is the curated list of top interview questions and answers in the OOPs.

Basic OOPs Interview Questions and Answers

Here is a rundown of the answers to the OOPs basic interview questions for beginners or professionals,

1) What is an Object-Oriented Programming language?

OOPs are abbreviated as ‘Object Oriented Programming systems’. The programming languages that execute objects and related processes following the Object-Oriented Programming paradigm or OOPs are known as Object-Oriented Programming languages.

Java, Python, C++, Lisp, and Perl are examples of popular object-oriented programming languages.

2) What are some major Object Oriented Programming languages?

Some of the major Object-Oriented Programming languages include:

- C++

- Java

- Javascript

- Python

- PHP, and many more.

3) What are the main features of OOPs?

Here are the main features of OOPs;

- Data Abstraction

- Encapsulation

- Inheritance

- Polymorphism

4) What are the core concepts of OOPS?

The OOPS core concepts are;

- Abstraction

- Association

- Aggregation

- Composition

- Encapsulation

- Inheritance

- Polymorphism

5) What is an Object?

An object is a basic run-time entity of an object-oriented system. It is an instance of a class and any count of instances of a class can be created. It has its own state, behavior, and identity. Objects are created from a user-defined or predefined template called a class.

6) What are the types of Inheritance in OOPS?

The different types of inheritances in OOps are as follows:

- Single Inheritance

- Multiple Inheritance

- Multi-level Inheritance

- Multi-path Inheritance

- Hierarchical Inheritance

- Hybrid Inheritance

Suggested Read: C# Interview Questions And Answers - UPDATED 2024

Advanced OOPs Interview Questions and Answers

Given below are the OOPs interview questions for freshers at an advanced level,

1) What are the 7 OOPs concepts?

The four main theoretical principles of object-oriented programming are abstraction, encapsulation, inheritance, and polymorphism.

Java operates with three further OOP concepts that are aggregation, association, and composition.

2) What is Structured Programming?

Structured Programming refers to an approach to program development that brings high-quality programs with definitive control flow.

This method highlights an approach that makes it easy to test, maintain, modify and debug.

Most programming paradigms comprise structured programming with the OOPs model.

3) What is encapsulation?

In OOPs concept, encapsulation is binding together the data and the functions that define, manipulate, and safeguard them from getters and setters under a single unit. One can apply encapsulation using access modifiers (public, private, and protected).

For example; make member variables of a class private and provide public getter and setter methods.

4) What is Polymorphism?

Polymorphism is derived from the Greek word “poly”, which means “many”, and “morph” “implying “form”.

In Object Oriented Programming system, polymorphism is the process of representing one form (a property, function, or object) in multiple forms.

It is divided into two types:

Method Overloading (compile time): also known as static binding and early binding.

Method Overriding (run time): also known as dynamic binding and late binding.

5) What are multiple inheritances?

Multiple inheritances is an inheritance type where a class inherits attributes and methods from more than one base class (or a parent class).

It has two class levels: base class and derived class.

6) What is the meaning of the “IS-A” and “HAS-A” relationship?

The “IS-A” is an inheritance relationship. The classes which inherit from the base classes are known as sub-classes or child classes (base object). 

Whereas, “HAS-A” is a composite relationship. One object that contains a reference to an occasion of another class of a similar class.

Intermediate Oops Interview Questions and Answers

Here are the OOPs practice questions with the answers at an intermediate level for experienced professionals or freshers,

1) What is a constructor?

A constructor is a special method of a class in a program that gets invoked implicitly when we create an object of the class.

It does not have any return type, cannot be overridden in Java, and cannot be inherited by the subclass.

There are two types of Constructors, 

Implicit Constructors: They are internally created in the .Net Framework.

Explicit Constructors: They can declare explicit constructors how we prefer.

2) What is a destructor?

A destructor is a method that cannot be manually involved in C#. It is automatically invoked when an object is to be destroyed.

The destructor clears allocated memory and free resources by closing the files and database connections of the object to allocate other processes.

It does not have a return type in C#, cannot be overloaded, and is public by default.

3) Is it possible for a class to inherit the constructor of its base class?

No, a class cannot inherit the constructor of its base class.

4) What are the types of constructors?

Each type of constructor differs from language to language.

Below are the feasible constructors accordingly:

- Copy constructor

- Default constructor

- Private constructor

- Parameterized constructor

- Static constructor

5) What is Interface?

The interface is an OOPs concept that contains methods but not their definitions. Interfaces, unlike classes, can only contain the signature of a class in C#. They do not contain detailed instructions or actions or any implementation.

Multiple interface inheritance with a single base is possible. You cannot create objects; any class that implements an interface defines the methods for the implementation of the interface.

6) What are access modifiers?

An access specifier is special types of keyword to specify or define the visibility and scope of entities or a class member in C#.

C# has four access modifiers as:

- Internal

- Protected

- Public

- Private

They play a crucial role in encapsulation.

Technical OOPs Interview Questions and Answers

Given below are the OOPs concepts interview questions along with answers at a technical level,

1) What is function overloading?

Function overloading is a process where there is a declaration of multiple functions with different parameters. It is an example of compile time polymorphism.

2) What is operator overloading?

Operator Overloading is a type of polymorphism to change the function or implement operators to achieve different tasks.

An operator is overloaded to give user-defined meaning to it.

3) What is the default access specifier in a class definition?

Private is the default access specifier in a class definition in C#.

4) What are virtual methods?

Virtual methods or virtual function is a method or function which is compulsorily declared with the virtual keyword.

The virtual keyword signifies that this method can be overridden by an inherited class using the override keyword to achieve polymorphism.

5) What are the operators that cannot be overloaded?

Below are the certain operators,

- Member Access or Dot Operator (.)

- Pointer to Member Operator (.*)

- sizeof operator

- Scope Resolution Operator (::)

- Ternary Operator (? :)

6) What are the advantages of OOPs?

The major advantages include,

- Code reusability via inheritance

- Data Security via Encapsulation

- Simple User Interface via Abstraction

- Structured Class Approach with objects to maintain code with easy detection of errors.

- Maintainability of objects

- Modifiability in an OO program

- Simple Structure

7) Explain multicast delegate?

A multicast delegate is a variable that has references from multiple functions. All the functions to which the multicast delegate referenced are going to be invoked when the multicast delegate is invoked.

The two to create  multicast delegate involves;

• + or += to subscribe to the method or function with the delegate.
• + or -= to unsubscribe the method or function with the delegate.

Conclusion

OOPs has a good call in business and with software publishers that demand skills to develop software as per their requirements. A career with OOPs knowledge is promising as the using the methodologies of OOPs is frequent.

OOPs interview questions and answers preparation course will bridge success to your next OOPs work.

A candidate must be subjectively prepared and go in hand with OOPs concepts for interview to crack the tricky OOPs interview questions.

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