What is Inheritance in Java? Here is Detail Explanation of Inheritance

What  Inheritance is? Perhaps for those who learning about object oriented programming (OOP) have heard about this concept. Maybe there are some people have understood about Inheritance or there are still confuse about how Inheritance really work.

This article will guide you who learning object oriented programming and still don't understand the concept of Inheritance.

What Inheritance is?

Inheritance is the process of inheriting data/method from super class to its sub class. What does it means? It means what is owned by super class (read : method/process) is also owned by its sub class.

What is the characteristic of class that use Inheritance concept?

The main characteristic that you can find is that class will use extends to its super class. For example :

	Class Tree{
	.....
	}
	Class Pine extends Tree {
	.....
	}

view raw Extends.java hosted with ❤ by GitHub

From the snippet above, Class Tree as Super Class and Class Pine as Sub Class. Whatever data/method/process that owned by Class Tree is also owned by Class Pine.

Is all extends means that class has implement Inheritance concept?

Basically yes, but we have to get the concept of Inheritance, why developers created Inheritance model? Have you thinking about it?

Inheritance concept created in order to make easy developers to access the same method/function in various classes by extends the super class.

But there are some things that must be thought out before you implement Inheritance in your project, here are they :

1. Make sure you have understood the flow of your program and its characteristic (is that related with the Car, People or the thing that have much entities inside it)
2. If you create a class that contains function/method, thought first, is that method will used much time in different classes or not
3. How often we will call the same method or function
4. How important the method or function in class where will use it.

If you requirements like the 4 point above, you should use the Inheritance concept. But if now, there is no problem with that, here we talk about the best practice implementation of Inheritance.

Example :

If you create super class called Class Tree, the create sub class called Class Yamaha, and then the Class Yamaha extends Tree{}. it totally wrong! We should extends that much related with the Super Class, not just do extends like what you will. haha

Until here, understood?

So, what is the right characteristic that can implement Inheritance concept?

There are much example that can implement the Inheritance concept, here I will give you one :

Characteristic of Hospital

Super Class :

• Class name : Hospital{...}
• Method : hospitalName(...), hospitalAddress(....)

Sub Class :

• Class name : Employee{...}
• Method : employeeName(...), employeeAge(....)

Perhaps one of you have a question and asking "What the relation of Class Employee and Class Hospital?"

Well, the sure thing is the hospital must have employees, right? either it doctor, back office, front office or other staff. Those employees must be have an identity (looks like idcard) where are they work, so Class Employee has to extends Class Hospital as its Super Class.

Project Example

In order make you clear understand the concept of Inheritance, let implement the characteristic of the Hospital above

Class Hospital

	/*
	* To change this license header, choose License Headers in Project Properties.
	* To change this template file, choose Tools | Templates
	* and open the template in the editor.
	*/
	package hs;
	/**
	*
	* @author androidbie.com
	*/
	public class Hospital {
	private String hospitalName;
	private String hospitalAddress;
	public Hospital(String hospitalName, String hospitalAddress) {
	this.hospitalName = hospitalName;
	this.hospitalAddress = hospitalAddress;
	}
	public Hospital() {
	}
	public String getHospitalName() {
	return hospitalName;
	}
	public void setHospitalName(String hospitalName) {
	this.hospitalName = hospitalName;
	}
	public String getHospitalAddress() {
	return hospitalAddress;
	}
	public void setHospitalAddress(String hospitalAddress) {
	this.hospitalAddress = hospitalAddress;
	}
	}

view raw Hospital.java hosted with ❤ by GitHub

Class Employee

	/*
	* To change this license header, choose License Headers in Project Properties.
	* To change this template file, choose Tools | Templates
	* and open the template in the editor.
	*/
	package hs;
	/**
	*
	* @author androidbie.com
	*/
	public class Employee extends Hospital{
	private String employeeName;
	private String employeeAge;
	private String employeeTitle;
	public Employee(String employeeName, String employeeAge, String employeeTitle) {
	this.employeeName = employeeName;
	this.employeeAge = employeeAge;
	this.employeeTitle = employeeTitle;
	}
	public Employee() {
	}
	public String getEmployeeName() {
	return employeeName;
	}
	public void setEmployeeName(String employeeName) {
	this.employeeName = employeeName;
	}
	public String getEmployeeAge() {
	return employeeAge;
	}
	public void setEmployeeAge(String employeeAge) {
	this.employeeAge = employeeAge;
	}
	public String getEmployeeTitle() {
	return employeeTitle;
	}
	public void setEmployeeTitle(String employeeTitle) {
	this.employeeTitle = employeeTitle;
	}
	}

view raw Employee.java hosted with ❤ by GitHub

Main Program

	/*
	* To change this license header, choose License Headers in Project Properties.
	* To change this template file, choose Tools | Templates
	* and open the template in the editor.
	*/
	package hs;
	/**
	*
	* @author androidbie.com
	*/
	public class Main {
	public static void main(String[] args) {
	//kita panggi si sub classnya
	// #1
	Employee pg = new Employee("Anree", "21", "Front Office");
	pg.setHospitalName("Hospital ABC"); //method super class
	pg.setHospitalAddress("Victoria Street No 78"); //method superclass
	//#2
	Employee pg1 = new Employee("John A", "26", "Doctor Specialist");
	pg1.setHospitalName("Hospital GGG"); //method super class
	pg1.setHospitalAddress("Roma, Italy"); //method superclass
	//Show ID Card #1
	System.out.println("ID Card");
	System.out.println("");
	System.out.println("Employee Name : \t\t" + pg.getEmployeeName());
	System.out.println("Title : \t\t" + pg.getEmployeeTitle());
	System.out.println("Hospital Name :\t" + pg.getHospitalName());//method superclass
	System.out.println("Hospital Address :\t"+ pg.getHospitalAddress());//method superclass
	System.out.println("");
	System.out.println("");
	//Show ID Card #2
	System.out.println("ID Card");
	System.out.println("");
	System.out.println("Employee Name : \t\t" + pg1.getEmployeeName());
	System.out.println("Title : \t\t" + pg1.getEmployeeTitle());
	System.out.println("Hospital Name :\t" + pg1.getHospitalName());//method superclass
	System.out.println("Hospital Address :\t"+ pg1.getHospitalAddress());//method superclass
	}
	}

view raw Main.java hosted with ❤ by GitHub

Take a loot at the codes above, method setHospitalName and setHospitalAddress called directly from its Super Class. Why? Because those methods will call repeated, so that methods wrote in its Super Class (Class Hospital).

The output of the program above is :

Okay that is the explanation about how Inheritance works, hope you'll understand. Thank you.