Lab #5 (Exercise 6-3)

Use objects in the Invoice application

Due Date: Wednesday of Week 2
10 points

In this lab, you'll create an Invoice class and construct objects from it as you convert the Invoice application to an object-oriented application.

If you downloaded the file, open the files named InvoiceApp.java and Validator.java that are in your computer or USB drive. If you don't have the files, copy and paste the codes below:

InvoiceApp class

import java.text.NumberFormat;
import java.util.Scanner;

public class InvoiceApp
{
    public static void main(String[] args)
    {
        // display a welcome message
        System.out.println("Welcome to the Invoice Total Calculator");
        System.out.println();  // print a blank line

        Scanner sc = new Scanner(System.in);
        String choice = "y";
        while(choice.equalsIgnoreCase("y"))
        {
            // get user entries
            String customerType = Validator.getString(sc,
                "Enter customer type (r/c):   ");
			double subtotal = Validator.getDouble(sc,
                "Enter subtotal:              ", 0, 10000);

            // calculate the discount amount and total
            double discountPercent = getDiscountPercent(subtotal, customerType);
            double discountAmount = subtotal * discountPercent;
            double total = subtotal - discountAmount;

            // format the values
            NumberFormat currency = NumberFormat.getCurrencyInstance();
            NumberFormat percent = NumberFormat.getPercentInstance();
            String sSubtotal = currency.format(subtotal);
            String sCustomerType = "";
            if (customerType.equalsIgnoreCase("r"))
            	sCustomerType = "Retail";
            else if (customerType.equalsIgnoreCase("c"))
            	sCustomerType = "College";
          	String sDiscountPercent = percent.format(discountPercent);
            String sDiscountAmount = currency.format(discountAmount);
            String sTotal = currency.format(total);

            // format and display the results
            String message = "Subtotal:         " + sSubtotal + "\n"
                           + "Customer type:    " + sCustomerType + "\n"
                           + "Discount percent: " + sDiscountPercent + "\n"
                           + "Discount amount:  " + sDiscountAmount + "\n"
                           + "Total:            " + sTotal + "\n";
            System.out.println();
            System.out.println(message);

            System.out.print("Continue? (y/n): ");
            choice = sc.next();
            System.out.println();
        }
    }

    static double getDiscountPercent(double subtotal, String type)
    {
        double discountPercent = 0.0;
        if (type.equalsIgnoreCase("r"))
        {
            if (subtotal >= 500)
                discountPercent = .2;
            else if (subtotal >= 250 && subtotal < 500)
                discountPercent =.15;
            else if (subtotal >= 100 && subtotal < 500)
                discountPercent =.1;
            else if (subtotal < 100)
                discountPercent =.0;
        }
        else if (type.equalsIgnoreCase("c"))
        {
                discountPercent = .2;
        }
        else
            discountPercent = .05;

        return discountPercent;
     }
}

Validator class

import java.util.Scanner;

public class Validator
{
    public static String getString(Scanner sc, String prompt)
    {
        System.out.print(prompt);
        String s = sc.next();  // read user entry
        sc.nextLine();  // discard any other data entered on the line
        return s;
    }

    public static int getInt(Scanner sc, String prompt)
    {
        int i = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            System.out.print(prompt);
            if (sc.hasNextInt())
            {
                i = sc.nextInt();
                isValid = true;
            }
            else
            {
                System.out.println("Error! Invalid integer value. Try again.");
            }
            sc.nextLine();  // discard any other data entered on the line
        }
        return i;
    }

    public static int getInt(Scanner sc, String prompt,
    int min, int max)
    {
        int i = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            i = getInt(sc, prompt);
            if (i <= min)
                System.out.println(
                    "Error! Number must be greater than " + min + ".");
            else if (i >= max)
                System.out.println(
                    "Error! Number must be less than " + max + ".");
            else
                isValid = true;
        }
        return i;
    }

    public static double getDouble(Scanner sc, String prompt)
    {
        double d = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            System.out.print(prompt);
            if (sc.hasNextDouble())
            {
                d = sc.nextDouble();
                isValid = true;
            }
            else
            {
                System.out.println("Error! Invalid decimal value. Try again.");
            }
            sc.nextLine();  // discard any other data entered on the line
        }
        return d;
    }

    public static double getDouble(Scanner sc, String prompt,
    double min, double max)
    {
        double d = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            d = getDouble(sc, prompt);
            if (d <= min)
                System.out.println(
                    "Error! Number must be greater than " + min + ".");
            else if (d >= max)
                System.out.println(
                    "Error! Number must be less than " + max + ".");
            else
                isValid = true;
        }
        return d;
    }
}

Start a new class named Invoice and save it in the same directory. Then, write the code for this class so it provides allof the data and all of the processing for an Invoice object. Its constructor should require the subtotal and customer type as its only paramters, and it should initialize instance variables for discount percent, discount amount, and invoice total. Its method should include the required get and set methods, plus a method named getInvoice that returns a string that contains all of the data for an invoice in a printable format. When you're done, compile the Invoice class.

Modify the code in the InvoiceApp class so it creates an Invoice object and uses its getInvoice method to get the formatted data for invoice. That should simplify this class considerably. Then, compile and test this class to make sure that this application works the way it did in step 1.

Include in your program the following comments:

Name of program
Team's name with all the names of the members (e.g. Team A: John Doe, Jane Smith, etc.)
Current Date
Computer system and compiler you are using
Brief description of the program

Compile and run the Java program.

Take a screen capture by hitting simultaneously the keys Alt and Print Screen (Prt Sc) of the output results (console) and paste it in MS Paint. Save it as a gif file.

When you are ready, upload the java programs (Invoice, InvoiceApp and Validator) by clicking the link below:

Upload Lab

I cannot grade if I don't get the files and receive your email.