Inheritance in Java

What is Inheritance ?

• Inheritance in Java means one class(parent) inherits (gets) properties and behaviors from another class(child).
• Child object behaving as a parent object.
• It helps in reusing code, saving time, and making programs more organized.

How to achieve inheritance?
Using extends keyword.

When you go for inheritance?
There is a IS-A relationship between two classes, we go for inheritance.
Real-Life Example
Scenatio 1:
A Vehicle is a parent class.
A Car is a child class.
Vehicle has common features like speed and fuel.
Car inherits these features and can have extra features like air conditioning.

class Vehicle {
    void move() {
        System.out.println("Vehicle is moving");
    }
}

class Car extends Vehicle {
    void honk() {
        System.out.println("Car is honking");
    }
}

public class Main {
    public static void main(String[] args) {
        Car c = new Car();
        c.move();  
        c.honk();  
    }
}

Output:

Vehicle is moving
Car is honking

Scenario 2:
Employee → Developer
Employee is a general concept
Developer is a specific type of employee
---> In real life, every developer is an employee, but not every employee is a developer.

class Employee {
    int id;
    String name;
    double salary;

    void work() {
        System.out.println("Employee is working");
    }
}

class Developer extends Employee {
    void code() {
        System.out.println("Developer is writing code");
    }
}

public class Company {
    public static void main(String[] args) {
        Developer dev = new Developer();
        dev.id = 101;
        dev.name = "Kumar";
        dev.salary = 60000;

        dev.work();   
        dev.code();   
    }
}
**Output:**

Employee is working
Developer is writing code

Why inheritance here?

• Common properties like id, name, salary belong to Employee
• Developer gets them automatically and adds its own behavior Important point:
• Car IS-A Vehicle relationship

Scenario 3:
Vehicle → Car
Vehicle is a parent (common features)
Car is a child (specialized vehicle)
---> Bike, car, bus are all vehicles.

class Vehicle {
    void start() {
        System.out.println("Vehicle is starting");
    }
}

class Car extends Vehicle {
    void playMusic() {
        System.out.println("Car is playing music");
    }
}

public class Transport {
    public static void main(String[] args) {
        Car car = new Car();
        car.start();       // from Vehicle
        car.playMusic();  // from Car
    }
}

Why inheritance?

• Avoid rewriting common logic like start()
• Child class focuses only on extra features