Programming Concepts. Andora Video is a small shop selling videos. The owner, Raul, wishes to develop a sales transaction processing system. The main objective of this system should be to display the total price of the sale after discounts, tax e.t.c.

        

System.out.println("Video Title?");

Scanner sc2 = new Scanner(System.in);

vdTitle = sc2.next();

        

System.out.println("Quantity?");

Scanner sc3 = new Scanner(System.in);

vdQty = sc3.nextInt();

        

System.out.println("vdPrice?");

Scanner sc4 = new Scanner(System.in);

vdPrice = sc4.nextDouble();

        

// Displaying the previously entered information

System.out.println("\n" +"Your Order details below...");

System.out.println("Video ID: "+ vdID);

System.out.println("Video Title: "+ vdTitle);

System.out.println("Video Price: "+ vdPrice);

System.out.println("Quantity: "+ vdQty);

                        

//Subtotal is calculated and displayed

double vdSubtotal = vdPrice * vdQty;

System.out.println("Subtotal: " + vdSubtotal);

                

        // Discount is calculated depending on the quantity

        if (vdQty >= 15)

        discount = disFor15Plus * vdSubtotal;

        else

        if (vdQty >= 10)

        discount = disFor10To14 * vdSubtotal;

        else

        if (vdQty >= 5)

        discount = disFor5To9 * vdSubtotal;

        else

        discount = 0;

                

//Discount is displayed

System.out.println("Discount: -" + discount);

                

// New subtotal is calculated after discount is subtracted

// Discounted Subtotal is Displayed        

double vdSubtotal2 = vdSubtotal - discount;

System.out.println("Discounted Subtotal:" + vdSubtotal2);

                

// VAT is calculated and added to new subtotal

double VAT = vdSubtotal2 * vatRate;        

double vdTotal = vdSubtotal2 + VAT;

//Final Total is displayed

System.out.println("Total inc VAT: " + vdTotal);

                

}

}

5. TESTING

1. Syntax Errors

After compiling and running my first attempt from the command prompt I encounter the following error.

The error message points me to the direction of line no. 55 and says there is a semi colon expected. Looking at the code, I can see at the end of the ‘if’ statement there is semicolon left out.

Logical Errors

As can be seen, there were no logical errors in this version.

8. VERSION 2

The second version shall have the ability to process multiple video titles in one transaction and also have some basic GUI features.

6. REQUIREMENTS

Input:                 String vdID, vdTitle, ask, indata

int vdQty,

double vdPrice,

final double         vatRate = .175, disFor15Plus = 0.25,

                disFor10To14 = 0.17, disFor5To9 = 0.12

Output:         String vdID, vdTitle,

int vdQty, itemCount, vdQtyAll,

double vdPrice, vdSubtotal, vdSubtotalAll, dSubtotal, vdTotal,                 discount, VAT

Process:        vdSubtotal = vdQty*vdPrice

                vdQtyAll +=vdQty

                vdSubtotalAll+=vdSubtotal

discount=vdsubtotalAll*disFor…

                dSubtotal=vdSubtotalAll-discount

VAT=dSubtotal*vatRate                

Total=dSubtotal+VAT

7. DATA TABLE

8. DESIGN PSEUDOCODE

        Declare vat and discount rates constants

Prompt for video ID, Title, Price and Quantity

Read inputted values

vdSubtotal = vdPrice*vdQty

Add vdQty to vdQtyAll

Add vdSubtotal to vdSubtotalAll

Display string asking if to continue

while ask = 'y' or 'Y'

repeat all above

while ask = 'n' or 'N'

display vdQtyAll

display vdSubtotalAll

if vdQtyAll >= 15

discount = disFor15Plus * vdSubtotalAll

if vdQtyAll >= 10

discount = disFor10To14 * vdSubtotalAll

if vdQtyAll >= 5

discount = disFor5To9 * vdSubtotalAll

else

discount = 0

display dSubtotal

display vdtotal

9. IMPLEMENTATION (v. 2)

import java.util.Scanner;

import javax.swing.JOptionPane;

public class VideoSales2

{

public static void main (String[] args)        

{

 

//Declaring Variables needed in the program and added values to the constants

               String ask="";

        double vdSubtotalAll=0;

        double vdQtyAll =0;

        final double vatRate = 0.175;

        String vdID, vdTitle, indata;

        int vdQty;

        double vdPrice, discount;

        final double disFor15Plus = 0.25;

        final double disFor10To14 = 0.17;

        final double disFor5To9 = 0.12;

       

// TODO code application logic here                

do

{

// GUI - ask for input from the user regarding video ID, Title, Quantity, Price

vdID=JOptionPane.showInputDialog("Video ID?");

        vdTitle=JOptionPane.showInputDialog("Video Title?");

       

                indata= JOptionPane.showInputDialog("Quantity?");

        //Convert indata string to integer

        vdQty= Integer.parseInt(indata);

       

        indata= JOptionPane.showInputDialog("Video Price?");

//Convert indata string to integer

        vdPrice= Double.parseDouble(indata);

        

//Display input to user

        System.out.println("\n"+"\n"+vdID);

        System.out.println(vdTitle);

        System.out.println("quantity=   "+vdQty);

        System.out.println("price = "+vdPrice+"\n"+"\n");

//Subtotal is calculated and displayed

double vdSubtotal = vdPrice * vdQty;

        

        //Current video quantity and subtotal is added to all previous         

        vdQtyAll+=vdQty;

        vdSubtotalAll+=vdSubtotal;

                

        //setting variable ‘ask’ to the answer of a question

        //variable needs to be inside of loop for the do while statement to work

ask=JOptionPane.showInputDialog("Repeat? y/n?");                

        

        }

        //Depending on the answer the TODO logic should repeat

        while(!(ask.equalsIgnoreCase("n")));

        

//Once loop is broken the whole video quantity and subtotal is displayed

        System.out.println("your total video quantity is: " +vdQtyAll);        

        System.out.println("Your subtotal is: " +vdSubtotalAll+"\n");

                

                // Discount is calculated depending on the quantity then displayed

                if (vdQtyAll >= 15)

                discount = disFor15Plus * vdSubtotalAll;

                else

                if (vdQtyAll >= 10)

                discount = disFor10To14 * vdSubtotalAll;

                else

                if (vdQtyAll >= 5)

                discount = disFor5To9 * vdSubtotalAll;

                else

                discount = 0;                

        

System.out.println("discount = " + discount);

//Concluding calculations are made and displayed

        double dSubtotal = vdSubtotalAll - discount;

        System.out.println("discounted subtotal: " +dSubtotal+"\n");        

                

        double VAT = dSubtotal * vatRate;

        

        System.out.println("VAT = " + VAT);

        double vdTotal = dSubtotal + VAT;

                

        System.out.println("Final total inc VAT ="+ vdTotal);

   

    }

}

10. TESTING

1. Syntax Errors

When attempting to build the program, the Netbeans IDE discovered two errors. The first error message points to line 97 and indicates a closing bracket is needed.

In the code I can select specific brackets and the IDE will highlight it’s pairing bracket. I do this and find that line 97 does not pair with the opening bracket after main; it instead pairs with the opening bracket to the ‘do while’ statement.

do

{

// GUI - ask for input from the user regarding video ID, Title, Quantity, Price

vdID=JOptionPane.showInputDialog("Video ID?");

vdTitle=JOptionPane.showInputDialog("Video Title?");

indata= JOptionPane.showInputDialog("Quantity?");

//Convert indata string to integer

vdQty= Integer.parseInt(indata);

indata= JOptionPane.showInputDialog("Video Price?");

//Convert indata string to integer

vdPrice= Double.parseDouble(indata);

        //Display input to user

        System.out.println("\n"+"\n"+vdID);

System.out.println(vdTitle);

System.out.println("quantity=   "+vdQty);

System.out.println("price = "+vdPrice+"\n"+"\n");

//Subtotal is calculated and displayed

double vdSubtotal = vdPrice * vdQty;

        //Current video quantity and subtotal is added to all previous         

        vdQtyAll+=vdQty;

        vdSubtotalAll+=vdSubtotal;        

        //setting variable ‘ask’ to the answer of a question

//variable needs to be inside of loop for the do while statement to work

ask=JOptionPane.showInputDialog("Repeat? y/n?");                

        

        //Depending on the answer the TODO logic should repeat

        while(!(ask.equalsIgnoreCase("n")));

I have clearly forgotten to close off the ‘do’ logic. Fixing this will probably solve the following error on line 100, because that is also a closing bracket. After adding this, I attempt to build the program again.

Unfortunately more errors are shown. These error messages point to two variables which it says may have not been initialized. More research into this shows that these variables have not been assigned an initial value so making a calculation from them is impossible. After assigning the value of ‘0’ to these variables, the programs compiles free of any errors.

Logical Errors – Order 1

The above test log shows no errors for the overall total of the multiple items in the order 1. No discount was subtracted because the overall quantity was below five.

Logical Errors – Order 2 (first attempt)

The overall total should be the overall price of the 8 DVDs minus the discount which would give us ‘113.4848’, then add the VAT which equals 133.34. However the result is well below that. The data I input may be incorrect, but if, on the second run the same problem arises, then there are a number of additional possibilities:-

• One of the constants have the incorrect figure assigned to them
• One of the logical operators are incorrect
• The calculations have been placed somewhere incorrect in the program
• An incorrect variable name used in a calculation

After running the program again and re-entering the data, I come to the same result. The IDE did not show us any error messages when compiling, so there must be a problem with the logic.

I first check the declared values of the constants, they seem to be fine. After isolating some parts of the program by commenting them out and compiling, I run the program to find all the calculations are correct. I therefore check the final total code which I had commented out for this purpose. I find the logical error to be contained in this line; the VAT had been subtracted rather than added.

2. Logical Errors – Order 2 (second attempt)

9. VERSION 3

The third and final version shall provide connectivity to a database, storing all the transactions. The order information shall be displayed in a GUI in the relevant numeric format.

11. REQUIREMENTS

Input:                 String vdID, vdTitle, ask, indata

int vdQty,

double vdPrice,

final double         vatRate = .175, disFor15Plus = 0.25,

                disFor10To14 = 0.17, disFor5To9 = 0.12

Output:         String vdID, vdTitle,

int vdQty, itemCount, vdQtyAll,

double vdPrice, vdSubtotal, vdSubtotalAll, dSubtotal, vdTotal,                 discount, VAT

Process:        vdSubtotal = vdQty*vdPrice

                vdQtyAll +=vdQty

                vdSubtotalAll+=vdSubtotal

discount=vdsubtotalAll*disFor…

                dSubtotal=vdSubtotalAll-discount

VAT=dSubtotal*vatRate                

Total=dSubtotal+VAT

12. DATA TABLE

13. DESIGN PSEUDOCODE

        Declare vat and discount rates constants

Prompt for video ID, Title, Price and Quantity

Read inputted values

vdSubtotal = vdPrice*vdQty

Add vdQty to vdQtyAll

Add vdSubtotal to vdSubtotalAll

Display string asking if to continue

while ask = 'y' or 'Y'

repeat all above

while ask = 'n' or 'N'

display vdQtyAll

display vdSubtotalAll

if vdQtyAll >= 15

discount = disFor15Plus * vdSubtotalAll

if vdQtyAll >= 10

discount = disFor10To14 * vdSubtotalAll

if vdQtyAll >= 5

discount = disFor5To9 * vdSubtotalAll

else

discount = 0

store vdID, vdTitle, vdQty, vdPrice in database

display dSubtotal

display vdtotal

14. FINAL IMPLEMENTATION (v. 3)

package videostore;

/**

 *

 * @author Kevin Abrahams

 */

import java.sql.*;

import java.text.NumberFormat;

import javax.swing.JOptionPane;

public class Main

{

    /**

     * @param args the command line arguments

     */

   

    public static void main(String[] args)         

{

               Connection connection;

           Statement statement;

String ask="";

        double vdSubtotalAll=0;

        double vdQtyAll =0;

        final double vatRate = 0.175;

        String vdID, vdTitle, indata;

        int vdQty;

        double vdPrice, discount;

        final double disFor15Plus = 0.25;

        final double disFor10To14 = 0.17;

        final double disFor5To9 = 0.12;

//Displays currency sign

NumberFormat money = NumberFormat.getCurrencyInstance();

       

// TODO code application logic here                

do

{

//Prompting for video detail variables

// GUI - ask for input from the user regarding video ID, Title, Quantity, Price

vdID=JOptionPane.showInputDialog("Video ID?");

vdTitle=JOptionPane.showInputDialog("Video Title?");

       

indata= JOptionPane.showInputDialog("Quantity?");

        //Convert indata string to integer

vdQty= Integer.parseInt(indata);

       

indata= JOptionPane.showInputDialog("Video Price?");

//Convert indata string to integer

vdPrice= Double.parseDouble(indata);

            try

            {

            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

            connection= DriverManager.getConnection("jdbc:odbc:VideoSales","","");

            statement = connection.createStatement();

            statement.executeUpdate("INSERT INTO tblVideoSales (VideoID,VideoTitle,Quantity,VideoPrice) VALUES ('"+ vdID+"','"+ vdTitle+"','"+ vdQty+"','"+vdPrice+"')");

            connection.close();

            }

            catch (Exception e)

            {

            System.err.println("Got an exception! ");

            System.err.println(e.getMessage());

            }

        System.out.println("\n"+"\n"+vdID);

        System.out.println(vdTitle);

        System.out.println("quantity=   "+vdQty);

        System.out.println("price = "+vdPrice+"\n"+"\n");

        double vdSubtotal = vdPrice * vdQty;

                

        vdQtyAll+=vdQty;        

        vdSubtotalAll+=vdSubtotal;

                

        ask=JOptionPane.showInputDialog("Repeat? y/n?");                

        

}

        while(!(ask.equalsIgnoreCase("n")));

        

        // Discount is calculated depending on the quantity then displayed                

        if (vdQtyAll >= 15)

        discount = disFor15Plus * vdSubtotalAll;

        else

        if (vdQtyAll >= 10)

        discount = disFor10To14 * vdSubtotalAll;

        else

        if (vdQtyAll >= 5)

        discount = disFor5To9 * vdSubtotalAll;

        else

        discount = 0;                

//Concluding calculations are made

        double dSubtotal = vdSubtotalAll - discount;

        double VAT = dSubtotal * vatRate;        

        double vdTotal = dSubtotal + VAT;

        

        //Concluding calculations displayed using GUI output message dialog box        

        JOptionPane.showMessageDialog(null,"The total video quantity is: " +money.format(vdQtyAll)+"\n"+"The subtotal is: "+money.format(vdSubtotalAll)+"\n"+"The discount is: " + money.format(discount)+"\n"+"The discounted subtotal is: "+money.format(dSubtotal)+"\n"+"The VAT is: " + money.format(VAT)+"\n"+"\n"+"The final total (inc VAT) is: "+ money.format(vdTotal));        

   

    }

}

15. TESTING

1. Database connectivity

In the control panel of windows it is necessary to go into the administrative tools and add a new data source (ODBC) in order for the program to have database connectivity.

After creating the driver for database connectivity, I compiled the program and it was error-free. However when running it, the following message appeared at the start of the data input process.

I found that data source name declared in the program was different to the actual data source just made. I changed the code as follows…

This worked and the following data successfully entered the relevant table in the database.

10. EVALUATION

I am satisfied that my application fulfils the basic user requirements; however it does leave room for improvement and further development. For example, it is able to process multiple video titles but I would like to, in the future, make the process of entering the video information easier by creating a better designed GUI.

The calculations all eventually passed the rigorous testing stage but the storing of these calculations rather than just the user input is another improvement that could be made. All the data together could then be displayed and even printed onto an itemised receipt.

I have left the program in a position in which the database functionality can be expanded on, to connect to a network. The program could even respond to scanned barcodes in relation to records held in the database.

11. CONCLUSION

The program is structured well with comments on all the major aspects, and I do believe that the above User Documentation is easy to understand and laid out in a good manner. The User Guide has screenshots to make the learning process easier.

This project was done under minimal supervision, and actually, I surprised myself in learning some of the key programming concepts by having to learn from and fix my own mistakes.

12. BIBLIOGRAPHY

1. BOOKS

• Deitel H. & P. (2001) Java How To Program 4th Edition, Prentice Hall
• McGrath, M. (2003) Java in easy steps, Computer Step
• Knott, G. & Waites, N. (2002) BTEC Nationals for IT Practitioners, Durham: BC Publications
• Parsons, J. J. & Oja, D. (2006) Computer Concepts, Sixth Edition, US: Course Technology Inc.
• Long, L. & N. (2005) Computers: Information Technology in Perspective 12th Edition, NJ: Pearson Education

2. WEBSITES

•  [Accessed 01 May 2008]
•  [Accessed 03 May 2008]
•  [Accessed 15 June 2008]
•  [Accessed 16 June 2008]

3. SOFTWARE

• Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007