Chapter 8, Problem 11PE

Explanation of Solution

Program:

File name: “Purchase.java”

//Define a class named Purchase

public class Purchase

{

    //Declare the private variables

    private int invoiceNumber;

    private double saleAmount;

    private double tax;

    private static final double RATE = 0.05;

    //Define a method to set the invoice number

    public void setInvoiceNumber(int num)

    {

        invoiceNumber = num;

    }

    //Define a method to set the amount of sale

    public void setSaleAmount(double amt)

    {

        saleAmount = amt;

        //Calculate the amount of sales tax

        tax = saleAmount * RATE;

    }

    /*Define a method to display the invoice number,

    amount of sale, and amount of sales tax*/

    public void display()

    {

        //Print the result

        System.out.println("Invoice #" + invoiceNumber +

         "  Amount of sale: $" + saleAmount + "  Tax: $" + tax);

    }

}

File name: “PurchaseArray.java”

//Import necessary header files

import java.util.*;

//Define a class named PurchaseArray

public class PurchaseArray

{

    //Define a main method

    public static void main(String[] args)

    {

        //Declare a purchases object

        Purchase[] purchases = new Purchase[5];

        //Declare the variables

        int num;

        double amount;

        String entry;

        //Create an object for Scanner class

        Scanner input = new Scanner(System.in);

        //Declare the variables and initialize the values

        int x;

        final int LOW = 1000, HIGH = 8000;

       //For loop to be executed until x exceeds 5

        for(x = 0; x < purchases.length; ++x)

        {

            purchases[x] = new Purchase();

            //Prompt the user to enter an invoice number

            System.out.print("Enter invoice number >> ");

            num = input...