Top 40+ OOPS Interview Questions With Answers for 2023
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Welcome back to our blog friends. In this post, we are going to tell you about more than 40+ OOPS Interview Questions And Answers With Examples. This question will help you during your programming interviews when the interviewer will ask you questions related to OOPs. So, if you are interested then stay tuned with us and if you will like our content then share it with your developer friends.
Basic Object-Oriented Programming concepts
OOP whose full form is Object-Oriented Programming is a very advanced topic for programming and has a lot of features like Encapsulation Enforces Modularity, Inheritance Passes, and more but there are only four concepts of OOP Inheritance, Encapsulation, Polymorphism, and Data abstraction and all of them are very important to learn because these are the basics and during your interview.
If you don't know about them then there are chances that you may fail your interview and you won't get the opportunity to work for your dream company like Microsoft, Google, Adobe, or any other big tech company.
I also recommend that before going in an interview you must prepare for Object-Oriented Programming because in interviews there are very high chances that the interviewers will ask you questions related to Object-Oriented Programming like What is OOP? Why do you need it? etc.
So, for you only we have found more than 40 questions that have a lot of chances to be asked to you during the interview and the best thing is that along with the questions we have also provided the answers that you can say during your interview.
1) What are constructors and how many types of constructors are there for Java?
Constructors in Java are particular methods used when an object is initialized but their main purpose is to initialize the data fields of an object in a class before it is used. Unlike Java methods, a constructor has the same name as the class and does not have any return type. Example -
public class MyClass{
//Constructor
MyClass(){
System. out.println("Oracle.com");
}
public static void main(String args[]){
MyClass obj = new MyClass();
//
}
}
2) What are other programming paradigms other than OOPs?
There are majorly four programming paradigms other than OOPs-
1. Imperative programming paradigms (best examples - C, Java, Pascal) and more.
2. Logical programming paradigms (best examples - Datalog and ASP (Answer Set Programming)) and more.
3. Object-Oriented programming paradigms (best examples - C++, C#, PERL, RUBY) and more.
4. Functional programming paradigms (best examples - Python, Haskell, Lisp, Erlang) and more.
3) What is SOP?
The full form of SOP is Structural Programming. It is a programming paradigm that aims to improve the clarity, quality, and development of time of a computer program, and to improve them it extensively uses the structured control flow constructs of selection (if/then/else) and repetition (while and for), blocks and more which makes it easier to learn than OOP and requires less time to write. In simple words, it aims to provide logical structure to a program when required.
4) What are the differences between OOP and SOP?
There are several differences between OOP and SOP during your interview it will be good to learn 5 differences between them -
1. Data in SOP is not as secure as that of an OOP
2. It is difficult to reuse code in SOP while it is easier to reuse code in OOP
3. There are no access specifiers in SOP while there are three types of access specifiers in OOP such as private, public, and protected
4. SOP is easier to code learn than OOP.
5. SOP divides the code into functions or modules while Java doesn't it works on the concept of objects which contains data in the form of fields and code in the form of procedures.
5) Tell me the difference between Compile time polymorphism and Runtime polymorphism?
The difference between both of them is that Compile time polymorphism can be achieved through static binding and Runtime polymorphism can be achieved through dynamic binding. Another difference between them is that in compile time polymorphism inheritance is involved while in runtime polymorphism inheritance is not involved.
6) Tell me the meaning of encapsulation?
According to sumlogic.com, it is a method of restricting direct access to some components of an object so that users cannot obtain state values for all variables of a specific object.
7) What is a class?
According to the TechTarget website a template definition of the methods and variables in a particular kind of object. Thus, it has real values instead of variables and due to which an object is a specific instance of a class and its true.
8) What is a constructor?
In (OOP) Object-oriented programming, it is a special method of a class or structure that initializes a freshly created object of that type. Thus it is called a constructor.
9) What is Abstraction?
Abstraction entails concealing the app's specifics from the outside world. In simple words, Hide the details of your app like name, code or images, etc from other people.
10) What is polymorphism?
Polymorphism is an important topic in the world of Object-oriented programming. In simple words, it is just a situation which occurs several times in various forms.
11) Why are OOPs so popular?
Oops, are really popular at this time because it solves a problem in a very simple way and helps their users or government in various ways.
12) Tell me the meaning of inheritance?
When one class uses a property of another class, this is known as inheritance, and it occurs when they have a similar implementation because the first class is based on another object.
13) Tell me the meaning of structured programming?
Structured programming also known as modular programming easier the creation of programs for you and helps you use readable and reusable code for developing your project.
14) What is an object?
They are the first things that come to mind when designing a program, as well as the units of code that are ultimately derived from the process called an object.
15) Is it always necessary to create objects from class?
Yes, without objects you cannot create objects from a class.
16) Tell me the most important object-oriented programming language?
Java is the most important object-oriented programming language.
17) Tell me the meaning of OOP?
The meaning of OOP is Object-Oriented programming. It has multiple languages and makes your work easier.
18) How much memory does a class use?
Classes don't occupy any memory space.
20) Tell me the main feature of OOP?
A feature of OOP is inheritance.
21) Tell me the need for OOPs?
The need for OOPs cannot be over-emphasized they are really important because it is a method that organizes your code for the highest reusability. It makes your work easier and is used in the form of languages in many fields like for creating apps, and games with help of languages like Java, C++, and C with the help of this you can contain objects that can interact with the user.
22) How does C++ support polymorphism?
In C++ polymorphism means the same institution acts in another way for different situations.
23) What are classes?
Classes, according to Brilliant.org, are blueprints for making objects. It provides initial values for state and behavior implementations, and it is also a very fundamental thing in OOP that you should know even though it is a very essential subject.
24) What are structures?
Structures, according to ques10.com, are nothing more than a collection of variables of the same or different data types; it includes classes, objects, and so on.
25) What are the main features of OOP?
There are three main features of Object-oriented programming. They are polymorphism, encapsulation, and inheritance.
26) What are the differences between classes and structures?
For this question, you can say two main differences -
1. Structures are value types and classes are reference types.
2. Structures use stack allocation and classes use heap allocation.
27) Name some programming languages which work on the concepts of OOP?
Java, Python, and C++ are some of the languages which work on the concept of OOPs.
28) Can we call the base class method without creating an instance?
In this case, the static method can be called without creating an instance. So, according to this yes we can do that.
29) What are the different types of inheritance?
There are three types of inheritance in OOPS they are -
1. Single inheritance
2. Multi-level inheritance
3. Multiple inheritances
30) What are multiple and multilevel inheritances and differentiate them?
Multiple inheritance is a feature of some object-oriented programming languages that allows an object or class to receive characteristics from more than one parent object or parent class while in multi-level inheritance there is the participation of more than one class.
31) What do you mean by superclass?
The class in OOPs from which the sub-class has come is called a superclass.
32) What are subclasses?
A class that has come from any other class, it is called a subclass.
32) What are the limitations of inheritance?
For this question, you can say about three disadvantages -
1. Improper use of it can lead to wrong answers to your coding-related problems.
2. It can lead to memory wastage.
3. The base class will affect all the other child classes in your code.
33) Is Java a completely pure OOP language?
No, it is not completely a pure OOP language. However, it supports all four pillars of the OOP language.
34) What is method overloading?
Method overloading is a type of polymorphism in Object-oriented programming.
35) What is method overriding?
A language feature that enables a subclass or child class to provide a particular implementation of a method that one of its superclasses or parent classes already provides.
36) What are the differences between Overloading and Overriding?
If the interviewer asks you this question then you can say three basic differences -
1. Method overloading is possible only in the same class while method overriding is possible in derived classes.
2. Method overloading is also known as static binding while method overriding is also known as dynamic binding.
3. Method overloading is used to apply compile-time polymorphism while method overriding is used to apply run-time polymorphism.
37) What is an abstract class?
An abstract class is a type of class that contains at least one abstract method.
38) What are the ways to achieve abstract class?
In Java abstract class can be classified into two -
Partial abstraction achievement - It can be achieved by the implementation of concrete methods.
Full abstraction achievement - It can be achieved by using interfaces with abstract types that define a class behavior.
There are a few points to remember to achieve abstract class -
1. The abstract keyword must be used to define an abstract class.
2. It can support both abstract and non-abstract techniques.
3. It cannot be created.
4. It can also have constructors and static functions.
5. It can have final methods, which require the subclass not to change the method body.
39) What are static and dynamic polymorphism?
Static polymorphism is a type of polymorphism that gathers information to call a method during compile time while dynamic polymorphism is a type of polymorphism that gathers information to call a method at runtime.
40) What are ‘access specifiers’?
Access specifiers define how the attributes and methods of a class can be accessed.
41) What is an interface?
According to the University of Utah, an interface is a programming structure/syntax that enables a computer to impose specific characteristics on an object. (class).
Conclusion
In this post, we have given you all the important questions that an interviewer can ask you for your interview with answers. We have tried that the answers should be short and to point. So, if you like our content and appreciate our efforts then kindly share our post with your developer friends.
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