CS 139 Algorithm Development
Lab07A: Practice with Ifs

Objectives

 After this lab, students will be able to use a java if/else statement and either nested if statements or compound conditions.

Background

 CS Card International is a credit card company which produces charge statements for its customers each month. This program will generate the appropriate statement amounts.

New Terms

 No new terms in this lab.

Materials

 Use CSCard.java as a starter for Part 3.
Submission
  • Complete the CodeBat exercises indicated below at http://codingbat.com. Be sure to include your instructor in your profile.
  • Submit CSCard.java and CSCard_Test.java via Blackboard.

Acknowledgment

 Adapted from a lab from the original textbook for the course.


Part 1 - Set Up
  1. Create a new folder named lab07a for this lab, on your Desktop or removable drive.

  2. Download a copy of CSCard.java to your folder from Blackboard.


Part 2 - Warmup

CodingBat is a web site that has practice programming problems. These are set up as individual methods. See the About page for more information.

  1. Go to www.codingbat.com. If you have not already done so, create an account (upper right hand part of the window). Log in and then go to Prefs. Fill in your name and then "Share" your account with your instructor by putting her/his e-mail address in the Share box.

  2. In Java Warm-Ups-1, do problems icyHot and loneTeen.
Part 3 - Charge Account Processing 

Write a program to prepare the monthly charge account statement for a customer of CS CARD International, a credit card company. The program should take as input the previous balance on the account and the total amount of additional charges during the month. The program should then compute the interest for the month, the total new balance (the previous balance plus additional charges plus interest), and the minimum payment due. Use CSCard.java as the starting point for your program.

Assume the interest is 0 if the previous balance was $0.00 or less.  If the previous balance was greater than 0 the interest is 2% of the total owed (previous balance plus additional charges). 

Calculate the minimum payment based on the table below: 

            $0.00             for a new balance less than $0
         new balance          for a new balance between $0 and $49.99 (inclusive)
           $50.00             for a new balance between $50 and $300 (inclusive)
    20% of the new balance    for a new balance over $300


So if the new balance is $38.00 then the person must pay the whole $38.00; if the balance is $128 then the person must pay $50; if the balance is $350 the minimum payment is $70 (20% of 350). The program should print the charge account statement in the format below. Print all amounts using the currency format.  (NOTE: formatting has been done for you.  Use the variables provided and keep all output statements exactly as in the .java file).

CS CARD International Statement
===============================

Previous Balance:     $
Additional Charges:   $
Interest:             $

New Balance:          $
 
Minimum Payment:      $
Make sure you understand how the calculations are done yourself before trying to program. Write the algorithm and test your algorithm with some data to see how it works.  Use at least four different examples to use for testing.  You want to be able to test each of the conditions shown above.
  1. Using the variables provided, code the input statements as described in the .java file.  You must insure that the program will not crash if the user enters a bad value.
  2. Finish the stubs for the calculateInterest and calculateMinPayment methods returning bogus values for interest and minimum payments.
  3. Code the rest of the main method as if the two calculate methods were finished and test. You should see that the code properly reads in a value for the balance and additional charges and ouputs the values in the correct format. NOTE: The numbers will be wrong until you finish your coding.
  4. For each calculation (interest and minimum payment), you should code the corresponding method.
  5. Create a test file to test each of the two calculation methods. Test the program with a variety of data. Include debit balance, credit balance, and 0 balance. Make sure that you test each of the branches of your if statement(s) and the boundary conditions (like 0 and 49.99).
  6. When you are sure that your code is working properly, run the main method using a variety of inputs (like you used in your tests). Make sure the output still looks okay.

Upload both programs (CSCard.java and CSCard_Test.java) to the Blackboard assignment.
Optional Part 4 - Cool Down Practice

Return to www.codingbat.com. In Java Logic-1, do squirrelPlay and answerCell.


last update - 10/08/2012 - NLH