Write a CashRegister class that can be used with the RetailItem class that you wrote in Chapter 6's Programming Challenge 4. The CashRegister class should simulate the sale of a retail item. It should have a constructor that accepts a RetailItem object as an argument. The constructor should also accept an integer that represents the quantity of items being purchased. In addition, the class should have the following methods: • The getSubtotal method should return the subtotal of the sale, which is the quantity multiplied by the price. This method must get the price from the RetailItem object that was passed as an argument to the constructor.
• The getTax method should return the amount of sales tax on the purchase. The sales tax rate is 6 percent of a retail sale.
• The getTotal method should return the total of the sale, which is the subtotal plus the sales tax.

Demonstrate the class in a program that asks the user for the quantity of items being purchased and then displays the sale’s subtotal, amount of sales tax and total.

Following are the code to this question:

import java.util.*; //import package for user input

class RetailItem//defining class RetailItem  

{

private String desc;//defining String variable

private int unit;//defining integer variable

private double prices;//defining double variable

RetailItem()//defining default Constructor

{

   //Constructor body

}

Output:

The Sub Total value: 199.75

The Sales Tax value: 11.985

The Total value: $211.735

Explanation:

In the above code three class "RetailItem, CashRegister, and Main" is defined, in the class "RetailItem", it defines three variable that is "desc, unit, and prices", inside the class "get and set" method and the constructor is defined, that calculates its value.

In the next step,  class "CashRegister" is defined, and inside the class parameterized constructor is defined, which uses the get and set method to return its value.  

In the next step, the main class is declared, in the main method two-class object is created and calls its method that are "getSubtotal, getTax, and getTotal".  

There is some technical error that's why full code can't be added so, please find the attached file of code.  

b. related objects

explanation:

data is stored in related objects in an access database.