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Introduction

 

Object-Oriented Programming or OOPs is a language using objects in programming. Usually, it uses objects as a primary source and implements them for 'what will happen' in the code. These objects are visible to users who perform tasks. Object-oriented programming helps implement real-world entities like inheritance and polymorphism in programming. It combines the data and the functions operating on them. Thus, other parts of the code cannot access this data except that function. 

 

Object-oriented programming (OOP) concepts are the basics of modern programming. Hence its demand is also increasing in the market. Read on to know about the basic and expert questions on OOPS that are asked. We have covered some trending and core topics that will prepare you for OOPS interview questions in 2023.

 

 

OOPS Interview Questions 

 

Whether you are a fresher or an experienced professional, you have to clear an interview round. Many times you are well-versed in practicals and lack theoretical knowledge. Similarly, you may be an expert in theoretical concepts, but can't respond quickly to programming questions. Here is a list of some questions that will make you job-ready in OOPS in 2023.

 

 

1. What Are The OOPS Core Concepts?

 

OOPS core concepts include Abstraction, Polymorphism, Encapsulation, Composition, Inheritance, Association, and Aggregation

 

 

2. Mention Some Advantages Of OOPS

 

  • OOPs, methodology enhances the code reusability. It saves development time.
  • Enables easy message passing for communication between classes and objects.
  • For code security, it uses functionalities like data abstraction and hiding. 
  • It uses inheritance to eliminate the need for code redundancy.
  • It exhibits a modular structure and is adaptable for easy maintenance.

 

 

3. What Are Encapsulation And Abstraction?

 

Encapsulation is an OOPS concept that creates and defines the permissions of an object, its member variables, and methods. Whereas, abstraction is also an OOPS concept that constructs the structure of real-world objects. 

 

Our Learners Also Read: Everything You Must Know About Iterator In Java

 

 

There are various OOP languages and the most widely used are Java, Go,

Python, Dart, C++ ,C# and Ruby

 

 

5. What Is Polymorphism?

 

It is the occurrence of anything in various forms. Java supports many forms of polymorphism. For instance, polymorphic return types, polymorphic reference variables, polymorphic methods, and polymorphic argument types.

 

 

6. What Is Inheritance?

 

In Inheritance, a subclass can inherit the states and behaviors of its superclass.

 

 

7. Explain The Purpose Of Using OOPs Concepts?

 

The purpose of OOP is to apply real-world concepts like hiding, inheritance, and polymorphism in programming. It binds together the data and the functions operating on them.  

 

 

8. Mention The Limitations Of OOPs

 

  • OOPs needs comprehensive testing processes.
  • The size of the programs created using an object-oriented approach may be larger than the programs written with the procedure-oriented programming approach.
  • It takes more time in solving problems as compared to Procedure Oriented Programming.
  • It requires a lot of pre-work and planning to develop software with this approach.
  • Not convenient for small problems.
  • OOP code is hard to understand without corresponding class documentation.

 

 

9. What Do You Understand By Class And Object? 

 

A class is a template of an object which is a user-defined data type. We define constants, variables, member functions, and other functions inside a class. At run time, it does not consume memory and is a logical entity.

 

An object is a real-world entity with behavior, attributes, and properties. It is an instance of the class. The object contains member functions, and variables defined in the class. It holds space in the memory. 

 

 

10. What Are The Operators In OOPs That Can’t Be Overloaded?

 

1. Dot access operator (.). It is also termed a member access operator.

2. Scope resolution operator (::)

3. Pointer to a member operator (. *)



 

Questions for Experienced 

 

 

1. Is Java A Pure Object Oriented Language? Explain.

 

Java is not a completely object-oriented programming language. It supports primitive data types like char, int, float, and double. These data types are stored as variables instead of the heap. Also, static methods can approach static variables without using an object. It does not happen in object-oriented concepts.

 

 

2. What Are The Types Of Inheritance?

 

 The Types of Inheritance include:

 

  • Single Inheritance

 

 The single-child class inherits features of the single-parent class.

 

  • Multiple Inheritance

 

Here, a class inherits features of more than one base class. The class can implement one or more interfaces.

 

  • Multilevel Inheritance

 

In multilevel inheritance, a class can inherit from a derived class and make it a base class for a new class. 

 

  • Hierarchical Inheritance

 

Here, a class is inherited by multiple subclasses.

 

  • Hybrid Inheritance

 

 Hybrid inheritance combines single and multiple inheritances.

 

 

3. What Is The Difference Between Structure And Class?

 

A structure is a user-defined collection of variables. It has different data types. Whereas, a class is a set of instructions to make a specific type of object.

 

 

4. What Is An Interface?

 

The interface is the same as the class where it can have methods and variables. However, its methods do not have a body. Method bodies are only for default and static methods. A class implements an interface. It also inherits the abstract methods of that interface.

 

 

5. How Is A Base Class Different From A Superclass?

 

The base class is the root class and the most generalized one. Whereas the superclass is the nearest parent class from which the other class inherits.

 

 

6. Explain The Different Access Modifiers In Java

 

Access modifiers in Java are responsible to control the access scope of methods, classes, constructors, variables, and data members. Below are the types of access modifiers in Java:

 

  • Default Access Modifier 

 

This modifier does not have access to specifier data members, classes, and methods. They are accessible within the same package.

 

  • Private Access modifiers 

 

They are marked with the keyword private. These modifiers are accessible only within the class. They are not even accessible by class from the same package.

 

  • Protected Access modifiers

 

They are accessible within the same package or subclasses from different packages.

 

  • Public Access Modifiers

 

They are accessible from everywhere.

 

 

7. How Many Types Of Constructors You Can Use In Java? 

 

There are Three Types of Constructors in Java. They are as follows:

 

  • Default Constructor

 

A default constructor is without any parameter. It invokes every time you create an instance of a class. 

 

  • No-arg Constructor

 

A no-arg constructor is a constructor without any argument.

 

  • Parameterized Constructor

 

It is a constructor with several parameters. You only have to provide arguments or initial values for the data type of parameters of the constructor.

 

These are some object-oriented programming interview questions for 2023. You can go through the basic and detailed theory of OOPS to perform well in your interviews. Usually, the interviewers pick more questions from what you have answered. Hence, be specific and answer the questions confidently

 

 

Conclusion

 

Oops, Concepts are applicable in various domains. Hence OOP’s demand is increasing in the market. We have tried to cover all the basic topics including the Top 10 OOPS interview questions and answers.  They also include the advantages and limitations of OOPS. You may have to answer and explain various concepts in the interview. For a better explanation, you can give real-life examples also. OOPS will be in demand in 2023, hence if you want to work with it, start preparing under the expert's guidance.