Top 60+ OOPS Interview Questions and Answers 2022

An object-oriented programming system or OOPS is a computer programming model that designs or arranges software for data, or more specifically, objects quite than functions and logic. An object can be defined as a data field that has unique attributes and behavior. This OOPS interview questions article will help you to know the unlike types of questions you might face in an consultation .

Top 60 OOPS Interview Questions in 2022

1. What is OOPs ?

OOPs stands for representing the Object-Oriented Programming system. Programs are treated as a collection of objects in oops. Each object is nothing but an example of a class .

2. difference between Procedural program and OOPs ?

procedural Programming is based on functions .

  • It shows the data to the entire program.
  • It does not have a scope for code reuse.
  • It follows the concept of top-down programming.
  • The nature of the language is complicated.
  • It is hard to modify, extend and maintain the code.
  • Object-oriented programming is based on real-world objects.
  • It encapsulates the data.
  • It provides more scope for code reuse.
  • It follows a bottom-up programming paradigm.
  • It is less complicated in nature, so it is easier to modify, extend and maintain.

3. Why use OOPs ?

OOPs has clearness in programming. It has tractability and simplicity in solving complex problems. Reuse of code is comfortable as the Inheri tance concept helps to reduce the redundancy of code. Data and code are bound in concert by encap sulation. OOPs has features for data concealment, so private data can be stored and keep confidentiality. Problems can be divided into different parts making it elementary to solve. The concept of polymorphism has flexibility for a unmarried entity can have multiple forms.

4. What are the basic concepts of OOPs ?

The basic concepts of OOPs are :

  • Inheritance
  • Encapsulation
  • Polymorphism
  • Abstraction

5. What is Encapsulation ?

encapsulation is besides a function of the OOPs concept. It refers to the bundle of data with the methods that operate on that datum. It besides helps to restrict any mastermind access to some of an aim ’ mho components .

6. What is Abstraction ?

Abstraction is an OOPs concept to build the structure of real-world objects. It “ shows ” alone necessity attributes and “ hides ” unnecessary data from the away. The main concentrate of abstraction is to hide unnecessary details from the users. It is one of the most authoritative concepts of OOPs .

7. What is method overloading ?

There is a concept where two or more methods can have the same name. But they should have different parameters, different numbers of parameters, different types of parameters, or both. These methods are known as overload methods and this sport is called method overloading .

8. What is method overriding ?

Method overriding is a concept of object-oriented program .
It is a lyric feature that allows a subclass or child class to provide a specific execution of a method which is already provided by one of its extremely classes or rear classes .

9. Types of Inheritance in OOPS

  • Hybrid Inheritance
  • Multiple Inheritance
  • Single Inheritance
  • Multi-level Inheritance
  • Hierarchical Inheritance

10. What is an object ?

object : An aim is an example of a class and besides It has its own identity and behavior .

11. What is Method?

It basically goes for describing the hardened of instructions and it is besides called a procedure .

12. What is a class?

class is a kind of user-defined data type that contains variables, properties, and methods. It besides helps to find the properties of an aim .

13. What are constructors?

The builder has the same name as the classify.
A builder is besides a special kind of method. It is used to initialize objects of the class .

14. Types of constructor

Types of constructors depend upon languages

  • Private Constructor
  • Default Constructor
  • Copy Constructor
  • Static Constructor
  • Parameterized Constructor

15. What is the difference between a class and a structure?

Class: Class is basically a User-defined blueprint from which objects are created. It consists of methods ( set of instructions ) that are performed on the objects .
Structure:  A structure is besides a user-defined solicitation of variables. Structures are besides different data types .

16. What are the access modifiers?

access modifiers or access specifiers are the keywords in object-oriented languages. It helps to set the approachability of classes, methods, and other members .

17. What languages come under the oops concept?

Simula is known as the first object-oriented programming lyric, the most popular OOP languages are :

  • Java
  • JavaScript
  • Python
  • C++
  • Visual Basic .NET.
  • Ruby
  • Scala
  • PHP

18. What is inheritance?

If you derive a class from another course that is known as inheritance .
The child class will inherit all the public and protected properties and methods from the parent classify. The child course can besides have its own properties and methods. An inherited class is defined by using the extends keyword .

19. What is hybrid inheritance?

A combination of multiple and multi-level inheritances is known as loanblend inheritance .

20. What is hierarchical inheritance?

Defining Hierarchical inheritance is basically when one base class has more than one subclasses. For example, the fruit class can have ‘ apple ’, ’ mango ’, ’ banana ’, ‘ cherry ’ etc. as its subclasses .

21. What are the limitations of inheritance?

It Increases the murder time and feat. It besides requires jumping bet on and forth between different classes. The parent classify and the child class are always tightly coupled. Afford modifications in the program would require changes for the parent and the child ’ south class. Inheritance requires careful execution otherwise it would lead to incorrect results .

22. What is a superclass?

A superclass or floor course is besides a class that works as a parent to some other class/ classes .
For example, the Vehicle class is a superclass of class Bike .

23. What is a subclass?

A subclass is a class that inherits from another classify. For model, the classify Bike is a subclass or a derive of the Vehicle class .

24. What is Polymorphism?

Polymorphism is one of the most use and the core concepts in OOP languages. It explains the concept of different classes can be used with the same interface. Each of these classes can have its own execution of the interface .

25. What is static polymorphism?

electrostatic polymorphism or static dressing is one kind of polymorphism that comes at compile clock time. An model of compile-time polymorphism is method overloading .

26. What is dynamic polymorphism?

Dynamic polymorphism, moral force ski binding, or Runtime polymorphism is besides part of polymorphism which is basically solved during runtime. An exemplar of runtime polymorphism : is method overriding .

27. What is operator overloading?

operator overload is used to implement operators using user-defined types, based on the arguments passed along with it .

28. Differentiate between overloading and overriding.

29. What is encapsulation?

encapsulation is used to wrap the datum and the code which works on in a unmarried unit together. case : encapsulation allows data-hiding as the data specified in one class is hidden from early classes .

30. What is the difference between public, private and protected access modifiers?

31. What is data abstraction?

Data abstractedness is one of the most important features of OOPs. It lone allows significant information to be displayed. It helps to hide the execution details .
For model, while using a fluid, you know, how can you message or call person but you don ’ thyroxine know how it actually happens .
This is data abstraction as the execution details are hidden from the exploiter .

32. How to achieve data abstraction?

Data abstraction can be achieved using two ways :

  • Abstract class
  • Abstract method

33. What is an abstract class?

An pilfer class is besides a class which is consists of abstract methods .
So what is an abstract method?
These methods are basically declared but not defined and If these methods need to be used later in some subclass that prison term those methods have to be entirely defined in the subclass .

34. Differentiate between data abstraction and encapsulation.

35. What are virtual functions?

virtual functions are besides part of the functions which are present in the parent class and they are overridden by the subclass .
These functions help to achieve runtime polymorphism .

36. What is a destructor?

A destructor is a method acting that is called mechanically when an object is destroyed .
The destructor besides recovers the batch space which was allocated to the destroy object. It besides start closing the files and database connections of the object, etc .

37. What is a copy constructor?

A replicate builder basically creates objects by copying variables from another object from the lapp class. The independent focus of a replicate builder is to make a new object from an existing

38. What is the use of ‘finalize’?

Finalize is used to free the unmanaged resources and besides help to clean before Garbage Collection ( GC ). It performs memory management tasks .

39. What is Garbage Collection(GC)?

garbage Collection is a separate of automatic pistol memory management. The Garbage collector helps to free the concern spaces by objects. Those spaces are no longer in being .

40. What is a final variable?

The final variable star does not change and It always refers to the same object by the property of non-transversity .

41. What is an exception?

An exception is a kind of message that interrupts and comes up when there is an issue with normal execution of a program. Exceptions provide an error and transfer that error to the exception animal trainer to resolve it. The state of the program is saved deoxyadenosine monophosphate soon as an exception is raised .

42. What is exception handling?

exception handling in Object-Oriented Programming is the most important concept. It is used to manage errors. An exception handler avail to throw errors and then catch the mistake in order to solve them .

43. What is the difference between an error and an exception?

44. What is a try/ catch block?

A try/ catch pulley helps to handle exceptions. The hear obstruct explains a bent of statements that may have an mistake. The capture block basically catches the exception .

45. What is a finally block?

A finally block executes when the test blockage exits and It besides executes even in case some unexpected exception is encountered. Finally block normally consists of some significant separate of the course of study .

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

Yes, you are allowed to call the foundation class without instantiating it but there are some conditions that are applicable :

  • If it is a static method
  • The base class is inherited by some other subclass

47. What is the difference between OOP and SOP?

Object-oriented program involves concepts of objects and classes. Everything is considered as an object which has specific properties and behaviors which are represented in a class. Object-oriented programming provides encapsulation and abstraction in the code. ex-husband : – Java Programming linguistic process .
Structure-oriented program involves the concepts of functions and structures. Everything is considered functionality and structures, represented using functions—Ex : – C Programming lyric .

48. What is the difference between a class and an object?

Any real-world entity is called an object. The object has specific properties and behaviors, and the similar type of objects having exchangeable features and behaviors are grouped as a class. Hence, Class is a blueprint of objects, and an object is an exemplify of a class .
x : – 1. An Animal is a class, and vomit, chase, and so forth, are objects with common properties like name, type, and common behaviors like speak, walking, running, etc .
2. Mobile is a class, and Nokia, moto, iPhone, and so forth, are objects with common properties like modal_no, discolor, and so forth, and common behaviors like audio_calling, video_calling, music, etc.

49. What are ‘access specifiers’?

access specifiers are the keywords in any programming linguistic process used to specify the Class ’ mho, method ’ second, interface ’ randomness and variable star ’ sulfur behavior concerning its handiness. The access specifiers in C++ Programming are populace, private, and protected .

50. Can you create an instance of an abstract class?

No, an example of Abstract class can not be created. To implement the outline Class, abstract methods, the Abstract Class should be extended by another class, and the object of the implementation course can be created .

51. What is an interface?

An interface is a user-defined datum type and is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface. A class describes an object ’ south attributes and behaviors, and an interface contains behaviors that a classify implements. The class represents “ how, ” and the interface represents “ what ’ .

52. What are pure virtual functions?

A pure virtual function/method is a routine whose implementations are not provided in the base course, and only a declaration is provided. The pure virtual function can have its execution code in the derived class ; otherwise, the deduce class will besides be considered an pilfer class. The class containing arrant virtual functions is pilfer .

53. Differentiate between a class and a method.

A course is a blueprint of objects, and it consists of the properties and behavior of the objects .
Methods are programming constructs that perform specific tasks/behavior .

54.  Differentiate between an abstract class and an interface?

An interface can have lone pilfer methods, but an abstraction classify can have abstract and non-abstract methods .
The interface should be used if merely the prerequisite specification is known and nothing about execution. If the implementation is known, but partially, then an pilfer course should be used. If the implementation is known completely, then concrete Class should be used .

55. What are the limitations of OOPs?

  1. Larger Program size – Programs can become lengthy if written using object-oriented programming concepts compared to procedure-oriented programming.
  2. Slower execution – As the number of lines of code to be executed is more comparatively, the execution time is also more.
  3. Not suitable for all types of Problems.
  4. Testing time is also higher for OOP Solutions.

56. What are the characteristics of an abstract class?

  1. A class having at least one pure virtual function is called an Abstract class.
  2. An Abstract class cannot have objects created, i.e., an abstract class cannot be instantiated, but Object references can be created.
  3. An Abstract class can have non-abstract functions and pure virtual functions also.
  4. The pure virtual function can have its implementation code in the derived class; otherwise, the derived class will also be considered an abstract Class

57. What is constructor chaining?

Constructor chain is a method acting to call one builder from another concerning a current object mention. It can be done in two ways : –

  1. Using the “this” keyword, the reference can be made to the constructor in the current class.
  2. To call the constructor from the base class “super” keyword will be used.

58. What is Coupling in OOP, and why is it helpful?

The degree of dependence between the components is called coupling .
Types of Coupling
A. Tight Coupling – If the addiction between components is high, these components are called tightly coupled .
ex-husband : –
Below three Classes are highly dependent on each other therefore they are tightly coupled .

class P
{
static int a = Q.j;
}
 
class Q
{
static int j = R.method();
}
 
class R
{
public static int method(){
return 3;
}

B. Loose Coupling – If the colony between components is low, it is called idle coupling. idle pair is preferred because of the be reasons : –

  1. It increases the maintainability of code
  2. It provides reusability of code

59. Name the operators that cannot be overloaded

All the operators except the + operator can not be overloaded .

60. What is Cohesion in OOP?

The modules having well-defined and specific functionality are called coherence .
Advantages
It improves the maintainability and reusability of code .

 61. What are the levels of data abstraction?

Highlighting the set of services by hiding inner execution details is called abstraction .
By using abstract Class and interface, we can implement abstraction

62. What are the types of variables in OOP?

Variables are basic units to store data in RAM for Java programs .
Variables should be declared before using them in Java programming. varying low-level formatting can be static or dynamic. The syntax for variable announcement and static low-level formatting is : –
Types of variables
1. primitive Variables
It is used to represent primitive values like int, float, etc .
2. address Variables
It is used to refer to objects in Java .
3. exemplify Variables
Variables whose value varied from object to object are case variables. For every object, a separate copy of the exemplify variable is created. case variables are declared within the class and outside any method/block/constructor
4. static variables
For static Variables, a individual imitate of the variable is created, and that replicate is shared between every class object. The inactive variable is created during class load and destroyed at class drop .
static variables can be accessed directly from the static and example area. We are not required to perform low-level formatting explicitly for static variables, and JVM will provide default values .
5. local anesthetic Variables
Variables declared inside a method acting or block or builder are local variables. Hence the setting of local anesthetic variables is the like as the stuff ’ s oscilloscope in which we declared that varying .
JVM doesn ’ triiodothyronine provide nonpayment values, and before using that variable, the low-level formatting should be performed explicitly .

OOPs Interview Questions FAQs

Q: What are the 4 basics of OOP? 
A: OOP stands for Object-Oriented Programming, and its four basic principles are Encapsulation, Abstraction, Polymorphism, and Inheritance. OOP enables programmers to consider software development as if they are working with actual entities. In OOP, some objects have a field where data/knowledge can be stored and can do respective methods .
Q: What is the object-oriented programming interview? 
A: Object-Oriented Programming, besides normally called OOPS, is a kind of programming that is more object-based and not just based on functions or procedures. person objects are collected into several classes. Real-world entities such as inheritance, polymorphism, and hiding are implemented by OOPS into programming. It besides enables binding data deoxyadenosine monophosphate good as code together .
Q: What are the 3 principles of OOP? 
A: The three main principles of Object-Oriented Programming are Encapsulation, inheritance, and polymorphism .
Q: What is the concept of OOPS?
A: OOPS or Object-Oriented Programming System is a programming concept that chiefly works based on Encapsulation, Abstraction, Polymorphism, and Inheritance. The usual concept of OOPs is to create objects, use them again all through the plan, and ultimately manipulate these objects to fetch our results .
Q: Why is OOPS used? 
A: The independent aim of an Object-Oriented program System is to implement real-world entities such as polymorphism, inheritance, shroud, and many more in program. The drive lies in binding together the datum a well as functions that work on them so that early parts of the code can not access the datum other than that function .
Q: What is polymorphism in OOPS? 
A: Polymorphism in an Object-Oriented program System is a feature of object-based program languages that enable a particular routine to use variables of respective types at different times. It can besides be called the ability of a program terminology to present the lapp interface for unlike primary data types .
Q: Who is the father of OOPS? 
A: The founder of the Object-Oriented Programming System is considered to be Alan Kay by some people. He identified some characteristics as basics to OOP Kay 1993:1. He coined OOPs around 1966 or 1967 when he was at grad school .
Q: What are the main features of OOPS? 
A: Some of the chief features in OOPS include Classes, Objects, Data Abstraction, Encapsulation, Inheritance, and Polymorphism. OOP is a programming paradigm that is based on the idea of objects .
Q: What are the advantages of OOPS?

A: Since OOP is one of the main development approaches which is easily accepted, the advantages are many. Some of the advantages of OOPS include Re-usability, Data Redundancy, Code Maintenance, Security, Design Benefits, Easy Troubleshooting, Better Productivity, Polymorphism Flexibility, and Problem-solving .
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besides Read Top 25 Common Interview Questions

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