🚀 Day 8 of My Automation Journey – Inheritance in Java (IS-A Relationship)

On Day 8, I learned one of the most powerful concepts in Java and OOP:

✅ Inheritance

This concept helps us reuse code and build real-world relationships between classes.

📌 What is Inheritance?

Inheritance is a mechanism where:

A child class acquires the properties and behavior of a parent class.

In simple words:

Child class extends Parent class

We use the keyword:

extends

📌 When Do We Use Inheritance?

We use inheritance when there is an:

🔁 IS-A relationship

Example:

Developer is an Employee

Car is a Vehicle

👉 In real life:
Every Developer is an Employee
But not every Employee is a Developer.

🔹 Program 1: Employee → Developer
✅ Parent Class

package inheritance;

public class Employee {

    int salary;

    void Welcome() {
        System.out.println("Welcome");
    }

    public static void main(String[] args) {

        Employee emp = new Employee();
        emp.salary = 20000;

        System.out.println(emp.salary);
        emp.Welcome();
    }
}

✅ Child Class

package inheritance;

public class Devloper extends Employee {

    public static void main(String[] args) {

        Devloper dev = new Devloper();
        dev.salary = 10000;

        System.out.println(dev.salary);
        dev.Welcome();
    }
}

🔍 Step-by-Step Explanation
🔹 Step 1: extends Keyword

public class Devloper extends Employee

This means:

Devloper automatically gets:

salary variable

Welcome() method

Without rewriting them.

🔹 Step 2: Object Creation

Devloper dev = new Devloper();

When this line runs:

1. Memory is allocated
2. Devloper object is created
3. It contains:

• Its own properties (if any)
• All Employee properties

🔹 Step 3: Accessing Parent Data

dev.salary = 10000;

Even though salary is declared in Employee,
Devloper can use it because of inheritance.

🔹 Step 4: Calling Parent Method

dev.Welcome();

Output:

Welcome

The method is coming from the parent class.

🎯 Why Do We Use Inheritance?

Without inheritance:

❌ You must rewrite salary, id, name in every class
❌ Code duplication
❌ Hard to maintain

With inheritance:

✅ Code reusability
✅ Clean structure
✅ Real-world modeling
✅ Easy maintenance

🔹 Program 2: Vehicle → Car

Let’s see another example.

✅ Parent Class

package inheritance_1;

public class Vehicle {

    String Car, Bicycle, Lorry, Bus, truck;

    void Welcome() {
        System.out.println("Welcome to the vehicle World");
    }

    public static void main(String[] args) {

        Vehicle Model = new Vehicle();
        Model.Car = "Benz";
        Model.Bicycle = "Hercules";
        Model.Lorry = "TATA";

        Model.Welcome();
    }
}

✅ Child Class

package inheritance_1;

public class Car extends Vehicle {

    public static void main(String[] args) {

        Car Model_1 = new Car();
        Model_1.Car = "bmw";

        System.out.println(Model_1.Car);
        Model_1.Welcome();
    }
}

🔍 What Happens Here?
When you create:

Car Model_1 = new Car();

Java:

1. Creates Car object
2. Also includes all Vehicle properties
3. Allows access to Welcome() method

Output:

bmw
Welcome to the vehicle World

🧠 Memory Understanding

When a child object is created:

[ Employee Data ]
[ Devloper Data ]

OR

[ Vehicle Data ]
[ Car Data ]

Parent part is always present inside child object.

🏗 Types of Inheritance in Java

1️⃣ Single Inheritance
2️⃣ Multilevel Inheritance
3️⃣ Hierarchical Inheritance

(Java does NOT support multiple inheritance with classes.)

⚡ Important Notes

✔ Inheritance improves reusability
✔ extends is used for classes
✔ Child gets public & protected members
✔ Constructors are not inherited (very important)

🎤 Real-World Thinking

Think like this:

Employee → Developer
Vehicle → Car
Animal → Dog
Account → SavingsAccount

This is how automation frameworks are designed.

In Selenium projects:

BaseClass → TestClass
WebDriverSetup → LoginTest
Utility → TestCases

Inheritance is heavily used.

🏁 Day 8 Key Takeaways

✅ Understood IS-A relationship
✅ Learned extends keyword
✅ Accessed parent variable in child
✅ Called parent method from child
✅ Saw real-world examples

👨‍🏫 Trainer: Nantha from Payilagam

🤖 A Small Note
I used ChatGPT to help structure and refine this blog while ensuring the concepts remain aligned with my trainer’s explanations.