Java Inheritance Example

Inheritance in Java is a class can be extends from a partent class and takes the properties and functions from the parents and also be able to override them. The example here demonstrates a parent class Customer and a child class VIPCustomer. Since VIP class extends from Customer, it doesn’t have to redefine some basic prperties such as customer ID, account name, and balance. It only defines the properties unique to VIP customers, discountRate in this case.

The Customer class
[code language=”java”]
public class Customer {

//fields
private int customerID;
private String accountName;
private double balance;

//constructor, takes 3 parameters
public Customer(int id, String name, double bal) {
customerID = id;
accountName = name;
balance = bal;
}

public void display() {
System.out.println("Customer ID: " + customerID);
System.out.println("Account Name: " + accountName);
System.out.println("Balance: $" + balance);
}
}
[/code]

The VIPCustomer class
[code language=”java”]
public class VIPCustomer extends Customer
{
//fields
double discountRate;

//constructor, takes 4 parameters
public VIPCustomer(int id, String name, double bal, double rate)
{
//Calling the parent class’s constructor
super(id, name, bal);
discountRate = rate;
}

public void display()
{
//Calling the parent’s class’s sdisplay method.
super.display();
System.out.println("Discount rate is " + discountRate );
}
}
[/code]

The TestCustmomers class to test the Inhertiance of the above two classes.
[code language=”java”]
public class TestCustomers
{
public static void main(String[] args)
{
//Creating a customer and a vip customer
Customer customer = new Customer(1001, "Nancy", 1000.23);
VIPCustomer vipCustomer = new
VIPCustomer(1002, "Jim", 3456.78, 0.15);

//Calling the display methods to print the info.
customer.display();
vipCustomer.display();
}
}
[/code]

The output of the TestCustomers class

Account Name: Nancy
Balance: $1000.23
Customer ID: 1002
Account Name: Jim
Balance: $3456.78
Discount rate is 0.15