OOP Interview Questions

Introduction to OOP Questions and Answers

OOP (Object-oriented Programming) is a programming paradigm that contains objects and fields to hold the data and methods to implement business logic. Each and every object can interact with each other based on their access level modifiers. The object-oriented paradigm is based on the classes and objects where objects are the classes’ instances and can be created in different ways. There are different object-oriented programming languages such as C++, C#, PHP, Ruby, Java, Python, etc. The main features of Object-oriented Programming techniques are Abstraction, Encapsulation, Inheritance, and Polymorphism. Most of the dynamic programming languages are based on OOPs principles.

Now, if you are looking for a job related to OOP, you need to prepare for the 2022 OOP Interview Questions. Every interview is different from the different job profiles, but still, to clear the interview, you need to have a good and clear knowledge of OOP. Here, we have prepared the important OOP Interview Questions and Answers, which will help you succeed in your interview. These OOP Interview questions are divided into parts are as follows:

Below are the 10 important 2022 OOP Interview Questions and Answers:

Part 1 – OOP Interview Questions (Basic)

This first part covers basic OOP Interview Questions and Answers.

1. What are the core concepts of OOP?

Answer:
The core concepts of OOP are Abstraction, Encapsulation, Inheritance, and Polymorphism. Abstraction is the process of concealing complex logic by defining the code in a separate private method by hiding its implementation. Whatever functionality needed to use can be called by using its method identifier to get the result.

The concept of encapsulation is nothing but a Class used to hide the fields that hold data and the methods to perform the functions that can be accessed based on the access modifier. Polymorphism is the process of defining the same method multiple times to utilize based on data types or arguments. There are two types of polymorphism which are called runtime polymorphism and compile-time polymorphism.

2. What is a Class in OOP?

Answer:
A Class in Object-oriented Programming is ideally called a template or a blueprint of an object. An object of its class type will have the same properties as defined in the implementation of Class. An object will always be a specific instance of a class. A Class can have different subclasses and superclasses. A class can be a child class, or a parent class depends on its declaration. A subclass can have all the properties that its superclass has, whereas the superclass cannot have the subclass’s properties. Another class can extend a class, and it will be called a parent class.

Let us move to the next OOP Interview Questions And Answer.

3. What is a constructor in OOP?

Answer:
A constructor is a method used to invoke the object creation process by initializing the object’s state. The name of the constructor should be the class’s name ideally and may vary depending on the type of programming language. A constructor must not have any return type.

4. What is the Destructor in OOP?

Answer:
This is the most common OOP Interview Questions which is asked in an interview. A Destructor is a method that is invoked when the object is destroyed or when its’ scope is about to end. The method will be called explicitly or implicitly based on the programming language used. In C++, the destructor needs to be called, whereas in Java, it is not needed, and a garbage collection mechanism will handle it.

5. What is an Abstract class in OOP?

Answer:
An abstract class is used to define at least one abstract method, but an object cannot be created from it.  Classes created using abstract classes are called derived classes. An abstract class will not contain implementation code in its base class. If an abstract class is forced to instantiate an object out of it, a compilation error will be thrown.

Part 2 –OOP Interview Questions (Advanced)

Let us now have a look at the advanced OOP Interview Questions.

6. What are multiple inheritances in OOP?

Answer:
Multiple inheritances are the process of extending the behaviors of multiple classes by a single class. It creates an ambiguous situation when runtime to decide which class’ behavior has to be executed. C++ supports multiple inheritances, whereas Java doesn’t support them. The ambiguity and complex issues create a diamond problem defined as extending which parent class upon extending multiple classes.

7. What is static and dynamic binding in OOP?

Answer:
Static binding is also called early binding, which happens at compile-time, whereas Dynamic binding is called late binding, which happens at the time of run time. An example of static binding is method overloading, and dynamic binding is method overriding. The process of binding for static, final and private methods will always be done at compile-time, whereas the overriding is done at runtime. The process of binding overloaded methods is called static, whereas overridden methods are called dynamic.

Let us move to the next OOP Interview Questions And Answer.

8. What is operator overloading in OOP?

Answer:
Operator overloading is sometimes called ad-hoc polymorphism, which is defined as different operators will have different mechanisms based on the placement of operators and the arguments. In operator overloading, the semantics of the programming language is redefined, which is not usually recommended. In the case of the Java programming language, it was decided by the creators not to use this feature as Java is a production language mostly.

9. What is exception handling in OOP?

Answer:
These are the frequently asked OOP Interview Questions which is asked in an interview. Exception handling is the feature available in most object-oriented programming languages, which are defined as the process of handling exceptions during the execution of program flow. The flow of execution should be altered based on the outcome of the exception of aroused. The general blocks of exception handling include try, catch and throw for most of the programming languages like C++, Java etc. In the try block, the code that needs to be executed will be placed, and the catch block will handle the exception, and the thrown block will return the type of exception and error if it can’t be handled. This is the safest way of handling applications to safeguard the flow of the working application.

10. What are the benefits of OOPS techniques?

Answer:
The OOPS concepts’ main benefits are modularity, extensibility, simplicity, reusability, maintainability, modifiability, etc. The complexity of the programming can be reduced, and the coding structure can be made clear. The different complex functionalities can be decoupled using different classes and implementation methods around the application. The reusability feature provides minor changes in the code whenever needed, which provides the adaptability for the code changes or functionality changes.

The objects of the different classes can be reused in different implementation classes to use their features completely. The maintenance process becomes easier if the code is maintained in an organised way.

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