Write short notes on class and inheritance in oops with example. [5]

Class and Inheritance in OOP with Example

Class

A class is a blueprint or template in Object-Oriented Programming (OOP) that defines the properties (attributes) and behaviors (methods) of objects. It acts as a logical entity that groups related data and functions.

Example:

class Student {
    // Attributes (data members)
    String name;
    int rollNo;

    // Methods (member functions)
    void display() {
        System.out.println("Name: " + name + ", Roll No: " + rollNo);
    }
}

Here, Student is a class with attributes (name, rollNo) and a method (display()).

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Inheritance

Inheritance is a mechanism in OOP where a new class (subclass or child class) inherits properties and methods from an existing class (superclass or parent class). It promotes code reusability and establishes a hierarchical relationship between classes.

Types of Inheritance:

1. Single Inheritance – A subclass inherits from only one superclass.
2. Multilevel Inheritance – A subclass inherits from another subclass.
3. Multiple Inheritance – A subclass inherits from multiple superclasses (not supported in Java but possible in C++ using interfaces).
4. Hierarchical Inheritance – Multiple subclasses inherit from a single superclass.

Example (Single Inheritance):

class Animal {  // Superclass
    void eat() {
        System.out.println("Eating...");
    }
}

class Dog extends Animal {  // Subclass (inherits from Animal)
    void bark() {
        System.out.println("Barking...");
    }
}

public class Main {
    public static void main(String[] args) {
        Dog d = new Dog();
        d.eat();   // Inherited from Animal
        d.bark();  // Own method
    }
}

Output:

Eating...
Barking...

Explanation:

• Dog inherits the eat() method from Animal.
• Dog also has its own method bark().
• This reduces code duplication and improves maintainability.

Advantages of Inheritance:

• Reusability – Code from the parent class can be reused.
• Extensibility – New features can be added without modifying existing code.
• Hierarchical Classification – Models real-world relationships (e.g., Dog is an Animal).

Disadvantages:

• Tight Coupling – Changes in the parent class may affect subclasses.
• Complexity – Overuse can make the program hard to understand.

Inheritance is a fundamental concept in OOP that helps in creating modular, scalable, and efficient programs.