Java Inheritance

What is Inheritance?

• Inheritance is a mechanism where one class gets the states and behaviors of another class.
• inheritance is: is-a relationship. That is, we use inheritance only if there is a is-a relationship between two classes.

Example:
Car is a Vehicle
Orange is a Fruit
Surgeon is a Doctor
Dog is an Animal
Developer is an Employee

• We can say, A child class uses features of a parent class.

What is Superclass and Subclass?

• Child class is called as subclass and the parent class is called as superclass.

What keyword is used to implement Inheritance?

• The extends keyword is used to perform inheritance in Java.

Superclass:

public class Employee {

    int employeeID;
    int salary;

    public static void main(String[] args) {

    }

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

Subclass:

public class Developer extends Employee {


    public static void main(String[] args) {
        Developer d1 = new Developer();

        d1.employeeID = 18426;
        d1.salary = 400000;
        System.out.println(d1.employeeID);
        System.out.println(d1.salary);
        d1.work();
        d1.devWork();
    }

    public void devWork(){
        System.out.println("Coding");
    }


}

Why do we use Inheritance?

• Code reuse
• Avoid duplication
• Easy maintenance
• Builds relationship between classes

What are the types of inheritance?

• Single Inheritance
• Multilevel Inheritance
• Hierarchical Inheritance
• Multiple Inheritance
• Hybrid Inheritance

Example with Real world scenario:

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.

Why inheritance?

• Common properties like id, name, salary belong to Employee.
• Developer gets them automatically and adds its own behavior.

Important point :

• Developer inherits employee properties using extends.

Vehicle → Car

• Vehicle is a parent (common features).
• Car is a child (specialized vehicle).
• Bike, car, bus are all vehicles.

Why inheritance?

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

Bank → SavingsAccount

• Bank provides common services.
• SavingsAccount is one specific account type.
• All accounts follow bank rules, but savings account has extra features.

Why inheritance?

• Common banking behavior in parent.
• Specific account rules in child.