Problem

You are a self-employed junior programmer. You've just started your own business and today, you've gotten your first job from a manager at a small arts and crafts store. The manager wants you to write a complete Java program that can be used by any cashier within her company to generate customer receipts for her convenience store which currently sells only three items.

First: The three items are brush sets, paint sets and primer. Since the prices of these materials will not change for a long time, you should use constants to store the cost of each of the three items and the tax rate.

Then, since the program is going to be used by multiple cashiers, use JOptionPane to prompt the user to enter:

The current cashier’s name
The quantity of each item.

The program will calculate and output:

The subtotal
Tax
Total.

As each item is entered, the program prints out the input given on a new line each time. After the quantity of the last item is entered, the program calculates a subtotal and prints it, then it prints out the tax value, and then calculates the subtotal plus tax as a final total and prints that value.

Now the program waits for the cashier to enter in a payment given amount. So now:

Prompt the cashier to enter a payment amount,
Calculate and print any change needed to be given back to the customer (if they overpaid) and
Round the change given to the nearest nickel and print that value.
Finally print out "Change given by: <cashier's name>"

Some details:

Constants: Store the cost of each item as a constant. Also, store the tax rate (7%) as a constant.

Input: Prompt the user to enter his/her name. Then use JOptionPane to input the quantity of each item. Finally use JOptionPane to input the amount of change given.

Calculate and Output:

The subtotal (the cost of the items without tax)
Tax
Total (of product plus taxes).

Also output the name of your store at the top of the receipt. When finding the change, use Math.ceil to round up so the customer gets the full change, and possibly more. For example, if the change due is 4.637, round to 4.64 using pennies and 4.65 using nickels.

Use Math.round() to round all output to two decimal spots.

If your input values were 2 brush sets ($8 each), 3 paint sets ($40 each), and 4 cans of primer ($18.75 each), and your cashier's name is Joni, your output should look like:

Welcome to ArtSupply.

Cashier: Joni
2 brush sets at $ 8.0
3 paint sets at $ 40.0
4 primer at $ 18.75
Product Total: $211.0
Tax: $ 14.77
Total = $ 225.77
Money received: $ 250.0
Change due: $ 24.23
Change rounded up to nearest nickel: $ 24.25
Change given by: Joni

The store manager wants you to use proper programming practices which happen to be exactly the same as the standards in Comp 1010.

Solution

Before you start writing code, you need to think about the problem in greater detail. Then you need to declare and initialize the variables you know you need. Finally you can program the problem in two parts: handling input, and obtaining output.

Break the Problem Down

While this problem is lengthier than others, the first rule of Computer Science is to break the problem into pieces. Ultimately we want the whole program done, but we need to break it into parts we can work on bit by bit. Start by reading the problem and figuring out what to do step by step.

Keep your Code Organized

The COMP 1010 Coding Standards give the foundation required to keep your code organized for this case study. You need to make sure your code is properly indented, variable names are properly named (as in: double change, as opposed to: double a) and all variables are initialized to zero or empty string constants which are "". Also, comments should always be included in your code.

Get it Done

Some programs will take longer than one sitting to complete. You must realize and accept that some programs can be done quickly, and other programs can take a very long time. No matter what you code, you will always have to deal with bugs. Start on your programs early enough and don't procrastinate. Leaving a program to the last minute — especially further on in the Computer Science degree — will cost you mentally and hurt your marks.

Part Zero: Declare Variables and Constants

Based on the problem description, we know we will need to use constants and use JOptionPane. JOptionPane requires that we store text in strings, so we must use strings. We're also dealing with integers and decimal value numbers which we will store as (doubles).

You will need to have two string variables. You also need three integer variables, six double variables and four double constants.

The string variables are for:

temporarily storing input strings for quantity
storing the cashier's name

The integer variables are to store the quantity of items bought. You will need one integer variable for each of the following :

Brushes
Paint sets
Primer

The double variables are for storing:

The tax
The subtotal of the bill
The total of the bill (this includes tax)
The total payment given
The total change returned
The total change given to the nearest nickel

The double constant variables are for storing:

The tax rate
The cost of the brushes
The cost of the paint
The cost of the primer

Part One: Handling Input

Now that you've completed the first task of setting up variables (and remembering to initialize them all to either 0 or empty string constants which are ""), the next task you want to do is print out "Welcome to ArtSupply". You can do this using System.out.println(). Then you want to prompt the user to enter their name. To do this, you need to use JOptionPane. Then you want to store the text entered in a string. This can be simply done roughly like this (you will need to fill in the parameters to the showInputDialog method):

StringVariable = JOptionPane.showInputDialog();

Once you have the text stored, you want to print out the string value and move the cursor to a new line. You can do this by using the System.out.println("<text>") function. Continue on by prompting the user to enter in 3 numbers using JOptionPane. Each time the user enters a number you want to convert the entered value to an integer and then print the numbers. The following code illustrates how to convert the entered value to an integer:

IntegerVariable = Integer.parseInt(StringVariable);

To print the numbers, you use System.out.println(<variable name>)

We can also assume that the user is entering a number and therefore we do not need to do any error checking.

Note for extended knowledge: to error check this code, you can take the input text and store it into a string. Then you can use a piece of code called a try catch block along with a NumberFormatException.

After the inputs are entered and properly stored, you need to do some math. Proceed by calculating the subtotal, tax and the total amount using simple math equations. After the values are calculated, print out the subtotal, the tax, the total amount. Make sure the output is in the same order as the output shown in the problem description.

You are now about half way done this program!

Part Two: Obtaining Output

Now the cashier is waiting for the customer to pay. Assuming the customer is not a thief, they would hand the cashier an amount greater than or equal to the total amount owing. This means you do not need to error-check to make sure the customer gives the cashier a proper amount (meaning that the customer did not shortchange the cashier). As you already know, you need to code your program to allow for this transaction to occur.

Note for extended knowledge: You can check to make sure that the amount of change you give to the cashier is greater than the total owing by using an if statement.

Use JOptionPane to prompt for an amount given, and then convert the string returned to a double (no error checking is needed). The following code shows how to convert a string to a double:

DoubleVariable = Double.parseDouble(StringVariable);

Print out the amount given. Calculate any change the cashier needs to give to the customer and print it out (even if it is $0.00). Round the amount of change to the nearest nickel and print that value.

Your code is now complete!

Post-programming Instructions

Now you may want to close your program, submit it and be happy that you're done! Unfortunately, reality doesn't work that way. You are only about half done with your program. Now you need to make sure your program works, and is up to standards. Below are a few steps you need to take when you feel you have finished your program.

Look it over

After your program is working, check for efficiency. This will come into play later on in the Computer Science degree, but you should practice doing it now. The next two sections are some methods to help you become more efficient.

Fix the Errors in the Code

If you have any bugs in your program, check them over and fix them!

Optimize the Code by Removing Unnecessary Variables

At the top of the main method, you should have a number of variables. If you have any more than what the above solution suggests, see if you can get rid of any extras you don't need.

Try to Break your Program

In this question, breaking your code would be easy to do unless you implement the error-checking procedures. You could easily break your code by entering in a letter instead of a number and trying to convert that string into an integer or double. However, if you do implement the error checking procedures in this program, and for your future programs, the best way to make sure you have complete and fantastic code is if you cannot make your program explode no matter what you do. The number one reason individuals are penalized for their code is because a random situation arises, even though it's highly unlikely to happen (but they do), and the programmer has not added the necessary code to handle the exception.

The Feeling of Hopelessness

There will be times that arise when you've gone too far down one path and your code is too far gone to fix properly. Understand that at times completely restarting the whole program over is a quicker and saner option than attempting to fix it properly. In other cases, backing up part way is more efficient. Make sure you save working versions of your program along the way. Lastly within this section, back up your code! If your computer dies and you lose your file, that's your responsibility!

Parting Statements

Remember that this is not the only "correct" way to do this program. There can be many different ways to accomplish this program and it can be further developed to handle error-checking from any aspect. Remember to code efficiently, accurately, and properly. This means: no more excess code than needed, know what you're trying to code and break it down as needed to accomplish parts of it at a time rather than the whole thing in one sitting, and comment and indent your code appropriately. Always remember to test your program as much as you possibly can, and practice, practice, practice! The more you code, the better you will become at it.

Code

Solution Code

import javax.swing.*;

/**....................................................................A1Q3
 * Print ticket invoice 
 * 74.101 SECTION L08/L09 
 * INSTRUCTOR  Terry Andres/Christina Penner
 * ASSIGNMENT  #1  QUESTION #2
 * @author C. Penner/T. Andres, 999999
 * @version 2004-Feb-09
 */
public class A1_Receipt {

  /**..................................................................main
   * PURPOSE: main reads items for a store, prints invoice, and calculates change
   * @param args is a list of command line arguments
   */
  public static void main (String [] args) {

    String inputString;  // for all inputs
    String name;

    int numBrush;        // number of brush sets
    int numPaint;        // number of paint sets
    int numPrimer;       //number primer
    double tax;          // calculated tax [$]
    double productTotal;   // subtotal of the bill [$]
    double total;        // total bill [$]
    double change;
    double pennyChange;
    double payment;

    final double TAX    = 0.07;  // rate; fraction of bill [-]
    final double BRUSH  = 8.00;  // adult ticket price [$]
    final double PAINT  = 40.00;  // children's ticket price [$]
    final double PRIMER = 18.75;  // rate, adult; improvement tax [-]

    //input cashier name
    name = JOptionPane.showInputDialog
    ("Enter Cashier name please");

    System.out.println("Welcome to ArtSupply. \nCashier: " + name);

    //input nummber brush sets
    inputString = JOptionPane.showInputDialog
    ("How many brush sets?");
    numBrush = Integer.parseInt(inputString);

    System.out.println(numBrush + " brush sets at $ " + BRUSH);

    //input nummber paint sets
    inputString = JOptionPane.showInputDialog
    ("How many paint sets?");
    numPaint = Integer.parseInt(inputString);

    System.out.println(numPaint + " paint sets at $ " + PAINT);

    //input nummber primer
    inputString = JOptionPane.showInputDialog
    ("How many primers?");
    numPrimer= Integer.parseInt(inputString);

    System.out.println(numPrimer + " primer at $ " + PRIMER);

    //calculate productTotal, levy, tax and total
    //round all above values to 2 decimal spots
    productTotal = ((numPaint*PAINT) + (numPrimer*PRIMER) + (numBrush*BRUSH));
    productTotal = Math.round (productTotal * 100) / 100.0;

    tax = TAX * ((numPaint*PAINT) + (numPrimer*PRIMER) + (numBrush*BRUSH));
    tax = Math.round (tax * 100)/100.0;

    total = productTotal + tax;
    total = Math.round (total * 100)/100.0;

    //output totals

    System.out.println ("Product Total: $" + productTotal);
    System.out.println ("Tax: $ "+ tax);
    System.out.println ("Total = " + total);


    //2B*****************************************************************

    //input payment
    inputString = JOptionPane.showInputDialog("Enter payment amount.");
    payment = Double.parseDouble(inputString);
    System.out.println("Money received: " + payment);

    //calculate change to nearest nickel
    change = payment - total;
    pennyChange = Math.round(change*100)/100.0;


    System.out.println("Change: " + change + "\nChange due: " + pennyChange);
    System.out.println("Change rounded up to nearest nickles: " + (Math.ceil(pennyChange*20)/20.0));
    System.out.println("Change given by: " + name);



    System.out.println("\nProgrammed by 1010 Instructors");
    System.out.println ("*** End of Processing ***");

  }
}

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Cash Receipt

Problem

Some details:

Solution

Break the Problem Down

Keep your Code Organized

Get it Done

Part Zero: Declare Variables and Constants

Part One: Handling Input

Part Two: Obtaining Output

Post-programming Instructions

Look it over

Fix the Errors in the Code

Optimize the Code by Removing Unnecessary Variables

Try to Break your Program

The Feeling of Hopelessness

Parting Statements

Code

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