OOP Interview Question

Basic Concepts:

1. What is Object-Oriented Programming (OOP)?
   • Answer: Object-Oriented Programming (OOP) is a programming paradigm that organizes software design around objects and data rather than actions and logic. It emphasizes modularity, encapsulation, inheritance, and polymorphism.
2. What are the four pillars of OOP? Can you explain each?
   • Answer:
     • Encapsulation: Bundling data and methods that operate on the data into a single unit (class) and restricting access to the data through abstraction.
     • Inheritance: Mechanism where a new class inherits properties and behaviors from an existing class, allowing for code reuse and hierarchical organization of classes.
     • Polymorphism: Ability of objects to take on multiple forms or have multiple behaviors depending on their context. It is achieved through method overriding and method overloading.
     • Abstraction: Process of hiding complex implementation details and exposing only the necessary features of an object.
3. Differentiate between a class and an object.
   • Answer:
     • A class is a blueprint or template for creating objects. It defines the properties (attributes) and behaviors (methods) that objects of the class will have.
     • An object is an instance of a class. It represents a specific realization of the class, with its own set of property values.
4. Explain the concept of inheritance.
   • Answer: Inheritance is a mechanism in OOP where a new class (derived or child class) inherits properties and behaviors from an existing class (base or parent class). It promotes code reusability and establishes a hierarchical relationship between classes.
5. What is encapsulation, and why is it important?
   • Answer: Encapsulation is the bundling of data and methods that operate on the data into a single unit (class). It helps in achieving data hiding, abstraction, and modularity, leading to better code organization, maintenance, and security.
6. Describe polymorphism and its types.
   • Answer: Polymorphism refers to the ability of objects to take on multiple forms or have multiple behaviors depending on their context. There are two types of polymorphism:
     • Compile-time polymorphism (static polymorphism): Occurs when the method to be invoked is determined at compile time. Examples include method overloading and operator overloading.
     • Runtime polymorphism (dynamic polymorphism): Occurs when the method to be invoked is determined at runtime. It is achieved through method overriding.
7. What is abstraction, and how is it achieved in OOP?
   • Answer: Abstraction is the process of hiding complex implementation details and exposing only the necessary features of an object. It is achieved in OOP through abstract classes and interfaces, which provide a blueprint for other classes to inherit from without specifying implementation details.
8. Define a constructor and a destructor in OOP.
   • Answer:
     • Constructor: A constructor is a special method in a class that is automatically called when an object of the class is created. It is used to initialize object properties and perform any necessary setup.
     • Destructor: A destructor is a special method in a class that is automatically called when an object is destroyed or goes out of scope. It is used to release any resources or perform cleanup operations before the object is deallocated from memory.
9. What is the difference between composition and inheritance?
   • Answer:
     • Composition: Composition is a design technique where a class contains an instance of another class as one of its members. It represents a “has-a” relationship between classes.
     • Inheritance: Inheritance is a mechanism where a class inherits properties and behaviors from another class. It represents an “is-a” relationship between classes.