JAVA EE: Java Tutorial : Inheritance in Java Example

Thursday, 13 August 2015

Java Tutorial : Inheritance in Java Example

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What is Inheritance in Java?

Inheritance is one of the core Object-Oriented Programming (OOP) concepts in Java. It allows one class to inherit properties (fields) and behaviors (methods) from another class.

By using the extends keyword, you establish an "IS-A" relationship between classes. This promotes clean architecture and code reusability.

Superclass vs. Subclass

Superclass (Parent Class): The class whose features are inherited. In our example, Employee is the superclass.
Subclass (Child Class): The class that inherits features from the superclass. In our example, SoftwareEngineer is the subclass.

Practical Example: Employee & SoftwareEngineer

A SoftwareEngineer is an Employee. Because SoftwareEngineer extends Employee, an instance of SoftwareEngineer can directly access the parent class properties like salary and methods like run() and walk(), along with its own unique property bonus and method talkAboutJava().

Key Takeaways

Use the extends keyword to implement inheritance in Java.
Child classes automatically acquire accessible fields and methods from the parent class.
Inheritance eliminates code redundancy and improves maintainability.

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Employee.java

/**
 * Employee class is the Super class.
 */
public class Employee
{
    int salary = 50000;

    public void run()
    {
        System.out.println("Can run");
    }

    public void walk()
    {
        System.out.println("Can Walk");
    }

}

SoftwareEngineer.java

/**
 * SoftwareEngineer class is the sub class which
 * extends Employee Super class.
 */
public class SoftwareEngineer extends Employee
{
    int bonus = 30000;
    
    public void talkAboutJava()
    {
        System.out.println("Can talk about Java");
    }
}

InheritanceExample.java

public class InheritanceExample
{
    public static void main(String[] args)
    {
        SoftwareEngineer softwareEngineer = new SoftwareEngineer();

        /*
         * SoftwareEngineer object can access the field and methods of own class
         * as well as of Employee class i.e. code reusability.
         */

        System.out.println("Properties");
        System.out.println("-----------------");
        System.out.println("SoftwareEngineer salary is:"
                + softwareEngineer.salary);

        System.out.println("Bonus of SoftwareEngineer is:"
                + softwareEngineer.bonus);

        System.out.println("\nBehaviours");
        System.out.println("-----------------");
        softwareEngineer.run();
        softwareEngineer.walk();
        softwareEngineer.talkAboutJava();

    }

}

Output

Properties
-----------------
SoftwareEngineer salary is:50000
Bonus of SoftwareEngineer is:30000

Behaviours
-----------------
Can run
Can Walk
Can talk about Java