Oops common interview questions and answers..

Here are some common OOPs interview questions and their answers:

1. What is OOP?

 Answer: OOP stands for Object-Oriented Programming. It is a programming paradigm that uses objects to represent and manipulate data. In OOP, data and functions that manipulate that data are grouped together into objects, which can then be reused and easily modified.

2. What are the four pillars of OOP?

Answer: The four pillars of OOP are encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: This is the process of hiding the implementation details of an object and exposing only the relevant information to the user.
• Inheritance: This is the process of creating new classes from existing classes. The new class inherits the properties and methods of the existing class and can also add new properties and methods.
• Polymorphism: This is the ability of objects of different classes to be used interchangeably. This can be achieved through method overloading or method overriding.
• Abstraction: This is the process of creating abstract classes or interfaces that define a set of methods without providing an implementation. This allows different classes to implement the same methods in different ways.

3. What is the difference between abstract class and interface?

Answer: An abstract class is a class that cannot be instantiated and can only be subclassed. It can have both abstract and non-abstract methods, and it can also have instance variables. An interface, on the other hand, is a collection of abstract methods and constants that can be implemented by any class. An interface cannot have instance variables.

4. What is polymorphism?

Answer: Polymorphism is the ability of objects of different classes to be used interchangeably. It can be achieved through method overloading or method overriding. Method overloading is when two or more methods in a class have the same name but different parameters. Method overriding is when a subclass provides its own implementation of a method that is already defined in its superclass.

5. What is inheritance?

Answer: Inheritance is the process of creating new classes from existing classes. The new class inherits the properties and methods of the existing class and can also add new properties and methods. Inheritance allows for code reuse and can make the code more modular and easier to maintain.

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

Answer: A class is a blueprint or template for creating objects, while an object is an instance of a class. A class defines the properties and methods that all objects of that class will have, while an object is a specific instance of that class with its own set of values for its properties.

7. What is encapsulation?

Answer: Encapsulation is the process of hiding the implementation details of an object and exposing only the relevant information to the user. This is achieved by using access modifiers such as private, public, and protected to control the visibility of the properties and methods of the object.

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

Answer: Private members are only accessible within the class that defines them. Public members are accessible from anywhere in the program. Protected members are accessible within the class that defines them and any subclasses.

9. What is method overloading?

Answer: Method overloading is when two or more methods in a class have the same name but different parameters. This allows the same method name to be used for different operations or data types.

10. What is method overriding?

Answer: Method overriding is when a subclass provides its own implementation of a method that is already defined in its superclass. This allows the subclass to modify or extend the behavior of the superclass method.