Top 50 2022 Interview Questions

Question 1

What is the difference between OOP and SOP?

Answer 1

Object-Oriented Programming
Object-Oriented Programming is a type of programming which is based on objects rather than just functions and procedures
Bottom-up approach, provides data hiding
Can solve problems of any complexity
Code can be reused thereby reducing redundancy

Structural Programming
Provides logical structure to a program where programs are divided functions
Top-down approach, does not provide data hiding
Can solve moderate problems, does not support code reusability

Question 2

What is Object Oriented Programming?

Answer 2

Object-Oriented Programming(OOPs) is a type of programming that is based on objects rather than just functions and procedures. Individual objects are grouped into classes. OOPs implements real-world entities like inheritance, polymorphism, hiding, etc into programming. It also allows binding data and code together.

Question 3

Why use OOPs?

Answer 3

OOPs allows clarity in programming thereby allowing simplicity in solving complex problems
Code can be reused through inheritance thereby reducing redundancy
Data and code are bound together by encapsulation
OOPs allows data hiding, therefore, private data is kept confidential
Problems can be divided into different parts making it simple to solve
The concept of polymorphism gives flexibility to the program by allowing the entities to have multiple forms

Question 4

What are the main features of OOPs?

Answer 4

Inheritance
Encapsulation
Polymorphism
Data Abstraction

Question 5

What is an object?

Answer 5

An object is a real-world entity which is the basic unit of OOPs for example chair, cat, dog, etc. Different objects have different states or attributes, and behaviors.

Question 6

What is a class?

Answer 6

A class is a prototype that consists of objects in different states and with different behaviors. It has a number of methods that are common the objects present within that class.

Question 7

What is the difference between a class and a structure?

Answer 7

Class: User-defined blueprint from which objects are created. It consists of methods or set of instructions that are to be performed on the objects.

Structure: A structure is basically a user-defined collection of variables which are of different data types.

Question 8

Can you call the base class method without creating an instance?

Answer 8

Yes, you can call the base class without instantiating it if:

It is a static method
The base class is inherited by some other subclass

Question 9

What is the difference between a class and an object?

Answer 9

Object
A real-world entity which is an instance of a class
Acts like a variable of the class
An object is a physical entity
Objects take memory space when they are created
Objects can be declared as and when required

Class
A class is basically a template or a blueprint within which objects can be created
Binds methods and data together into a single unit
A class is a logical entity
A class does not take memory space when created
Classes are declared just once

Question 10

What is inheritance?

Answer 10

Inheritance is a feature of OOPs which allows classes inherit common properties from other classes. For example, if there is a class such as ‘vehicle’, other classes like ‘car’, ‘bike’, etc can inherit common properties from the vehicle class. This property helps you get rid of redundant code thereby reducing the overall size of the code.

Question 11

What are the different types of inheritance?

Answer 11

Single inheritance
Multiple inheritance
Multilevel inheritance
Hierarchical inheritance
Hybrid inheritance

Question 12

What is the difference between multiple and multilevel inheritance?

Answer 12

Multiple Inheritance
Multiple inheritance comes into picture when a class inherits more than one base class
Example: A class defining a child inherits from two base classes Mother and Father

Multilevel Inheritance
Multilevel inheritance means a class inherits from another class which itself is a subclass of some other base class
Example: A class describing a sports car will inherit from a base class Car which inturn inherits another class Vehicle

Question 13

What is hybrid inheritance?

Answer 13

Hybrid inheritance is a combination of multiple and multi-level inheritance.

Question 14

What is hierarchical inheritance?

Answer 14

Hierarchical inheritance refers to inheritance where one base class has more than one subclasses. For example, the vehicle class can have ‘car’, ‘bike’, etc as its subclasses.

Question 15

What are the limitations of inheritance?

Answer 15

Increases the time and effort required to execute a program as it requires jumping back and forth between different classes
The parent class and the child class get tightly coupled
Any modifications to the program would require changes both in the parent as well as the child class
Needs careful implementation else would lead to incorrect results

Question 16

What is a superclass?

Answer 16

A superclass or base class is a class that acts as a parent to some other class or classes. For example, the Vehicle class is a superclass of class Car.

Question 17

What is a subclass?

Answer 17

A class that inherits from another class is called the subclass. For example, the class Car is a subclass or a derived of Vehicle class.

Question 18

What is polymorphism?

Answer 18

Polymorphism refers to the ability to exist in multiple forms. Multiple definitions can be given to a single interface. For example, if you have a class named Vehicle, it can have a method named speed but you cannot define it because different vehicles have different speed. This method will be defined in the subclasses with different definitions for different vehicles.

Question 19

What is static polymorphism?

Answer 19

Static polymorphism (static binding) is a kind of polymorphism that occurs at compile time. An example of compile-time polymorphism is method overloading.

Question 20

What is dynamic polymorphism?

Answer 20

Runtime polymorphism or dynamic polymorphism (dynamic binding) is a type of polymorphism which is resolved during runtime. An example of runtime polymorphism is method overriding

Question 21

What is method overloading?

Answer 21

Method overloading is a feature of OOPs which makes it possible to give the same name to more than one methods within a class if the arguments passed differ.

Question 22

What is method overriding?

Answer 22

Method overriding is a feature of OOPs by which the child class or the subclass can redefine methods present in the base class or parent class. Here, the method that is overridden has the same name as well as the signature meaning the arguments passed and the return type.

Question 23

What is operator overloading?

Answer 23

Operator overloading refers to implementing operators using user-defined types based on the arguments passed along with it.

Question 24

Differentiate between overloading and overriding.

Answer 24

Overloading
Two or more methods having the same name but different parameters or signature
Resolved during compile-time

Overriding
Child class redefining methods present in the base class with the same parameters/ signature
Resolved during runtime

Question 25

What is encapsulation?

Answer 25

Encapsulation refers to binding the data and the code that works on that together in a single unit. For example, a class. Encapsulation also allows data-hiding as the data specified in one class is hidden from other classes.

Question 26

What are ‘access specifiers’?

Answer 26

Access specifiers or access modifiers are keywords that determine the accessibility of methods, classes, etc in OOPs. These access specifiers allow the implementation of encapsulation. The most common access specifiers are public, private and protected. However, there are a few more which are specific to the programming languages.

Question 27

What is data abstraction?

Answer 27

Data abstraction is a very important feature of OOPs that allows displaying only the important information and hiding the implementation details. For example, while riding a bike, you know that if you raise the accelerator, the speed will increase, but you don’t know how it actually happens. This is data abstraction as the implementation details are hidden from the rider.

Question 28

How to achieve data abstraction?

Answer 28

Data abstraction can be achieved through:

Abstract class
Abstract method

Question 29

What is an abstract class?

Answer 29

An abstract class is a class that consists of abstract methods. These methods are basically declared but not defined. If these methods are to be used in some subclass, they need to be exclusively defined in the subclass.

Question 30

Can you create an instance of an abstract class?

Answer 30

No. Instances of an abstract class cannot be created because it does not have a complete implementation. However, instances of subclass inheriting the abstract class can be created.

Question 31

What is an interface?

Answer 31

It is a concept of OOPs that allows you to declare methods without defining them. Interfaces, unlike classes, are not blueprints because they do not contain detailed instructions or actions to be performed. Any class that implements an interface defines the methods of the interface.

Question 32

Differentiate between data abstraction and encapsulation.

Answer 32

Data abstraction
Solves the problem at the design level
Allows showing important aspects while hiding implementation details

Encapsulation
Solves the problem at the implementation level
Binds code and data together into a single unit and hides it from the world

Question 33

What are virtual functions?

Answer 33

Virtual functions are functions that are present in the parent class and are overridden by the subclass. These functions are used to achieve runtime polymorphism.

Question 34

What are pure virtual functions?

Answer 34

Pure virtual functions or abstract functions are functions that are only declared in the base class. This means that they do not contain any definition in the base class and need to be redefined in the subclass.

Question 35

What is a constructor?

Answer 35

A constructor is a special type of method that has the same name as the class and is used to initialize objects of that class.

Question 36

What is a destructor?

Answer 36

A destructor is a method that is automatically invoked when an object is destroyed. The destructor also recovers the heap space that was allocated to the destroyed object, closes the files and database connections of the object, etc.

Question 37

Types of constructors

Answer 37

Types of constructors differ from language to language. However, all the possible constructors are:

Default constructor
Parameterized constructor
Copy constructor
Static constructor
Private constructor

Question 38

What is a copy constructor?

Answer 38

A copy constructor creates objects by copying variables from another object of the same class. The main aim of a copy constructor is to create a new object from an existing one.

Question 39

What is the use of ‘finalize’?

Answer 39

Finalize as an object method used to free up unmanaged resources and cleanup before Garbage Collection(GC). It performs memory management tasks.

Question 40

What is Garbage Collection(GC)?

Answer 40

GC is an implementation of automatic memory management. The Garbage collector frees up space occupied by objects that are no longer in existence.

Question 41

Differentiate between a class and a method.

Answer 41

Class
A class is basically a template that binds the code and data together into a single unit. Classes consist of methods, variables, etc

Method
Callable set of instructions also called a procedure or function that are to be performed on the given data

Question 42

What is a final variable?

Answer 42

A variable whose value does not change. It always refers to the same object by the property of non-transversity.

Question 43

What is an exception?

Answer 43

An exception is a kind of notification that interrupts the normal execution of a program. Exceptions provide a pattern to the error and transfer the error to the exception handler to resolve it. The state of the program is saved as soon as an exception is raised.

Question 44

What is exception handling?

Answer 44

Exception handling in Object-Oriented Programming is a very important concept that is used to manage errors. An exception handler allows errors to be thrown and caught and implements a centralized mechanism to resolve them.

Question 45

What is the difference between an error and an exception?

Answer 45

Error
Errors are problems that should not be encountered by applications

Exception
Conditions that an application might try to catch

Question 46

What is a try/ catch block?

Answer 46

A try/ catch block is used to handle exceptions. The try block defines a set of statements that may lead to an error. The catch block basically catches the exception.

Question 47

What is a finally block?

Answer 47

A finally block consists of code that is used to execute important code such as closing a connection, etc. This block executes when the try block exits. It also makes sure that finally block executes even in case some unexpected exception is encountered.

Question 48

What are the limitations of OOPs?

Answer 48

Usually not suitable for small problems
Requires intensive testing
Takes more time to solve the problem
Requires proper planning
The programmer should think of solving a problem in terms of objects