CMSC 206 (Data Structures)

Assignment#2

Due:  September 24, 2012 11:59:59pm

The goal of this assignment is to develop your ability to do object-oriented programming, focusing specifically on developing and using a basic class. 

Over the next two assignments, you will write a program that allows a user to repeatedly create and manage credit card accounts.  In this assignment, we will focus on developing a basic class to represent the credit card.

When a new credit card account is opened, the credit company sets a credit limit for the user that specifies the maximum balance allowed on the account.  Unlike a debit card, the balance starts at $0.  The user can make purchases and charge them to the credit card, increasing the balance.  For example, if I charge two purchases of $100 and $50, my credit card balance would be $150.  Say that my credit limit is $500.  If I then tried to charge another $400 purchase to the card, the card would be declined since that would put the balance over my credit limit.  At the end of each month, the user must pay the entire balance on the card, or else the credit company charges the user interest on the balance.

• Implement a class CreditAccount that includes the following attributes and methods at a minimum (you can add others of your own design):
• Private Variables:  accountNumber, accountBalance, creditLimit, interestRate.
• The interest rate should be set to 1.25%, and the credit limit to $4,000.  While we won't change them in this assignment, they must be variables.
• A constructor that takes in one integer for the accountNumber, and initializes the accountNumber to the given value.
  
• Accessors (i.e., getters) for all private variables needed outside the class with appropriate public (or protected) access levels.
• A toString() function that outputs a textual description of the account that includes the account number, balance, credit limit and interest rate.
• The following two methods:
• void charge(double amount) which takes in an amount to charge against the account and throws an exception if this amount would push the balance over the credit limit.  This exception should be properly handled in the calling code.  The method should also output a simple status message to System.out, such as "Charging $40 to Account #101".
  
• void makePayment(double amount) which reduces the balance by the specified amount.  This method is also responsible for assessing interest on the balance if it is not paid in full.  Note that this interest should be assessed against the balance prior to the amount being paid off.  For example, if the balance is $200 and the user pays $50, 1.25% interest would be assessed against $200.  The method should also output a simple status message to System.out, such as "Received payment of $40 to Account #101".
• Be sure to do error checking on the inputs.  Negative payments and charges are not allowed, although the user can carry a minimum balance.
• Since we're working with money, all decimals need to be rounded off to two decimal places.  You can achieve this by multiplying a decimal by 100, rounding using Math.round(), and then dividing the result by 100.0.  I suggest making a function to do this, since you will need to do it a lot.
• Write a main() method within the CreditAccount class to demonstrate its functionality.  The main() method should perform the following tasks (in-order):

1. Print out your name to System.out along with the string " CS 206 Assignment 2".
   
2. Instantiate a new instance of the CreditAccount class
3. Print out a description of the account, including account number, balance, credit limit and interest rate, by calling the toString() method on it.
4. Charge $100 to the account (automatically printing out the corresponding status message of what was done to the account)
   
5. Print out the current balance (which should be $100)
6. Make a payment of $100 to the account (automatically printing out the corresponding status message of what was done to the account)
7. Print out the current balance (which should be $0)
8. Charge $100 to the account
9. Print out the current balance (which should be $100)
10. Make a payment of $50 to the account
11. Print out the current balance (which should be $51.25, including the unpaid portion and the interest)
12. Make a payment of $51.25 to the account
13. Print out the current balance (which should be $0)
14. Charge $-100 to the account, which should display an error message via an Exception
15. Make a payment of $-100, which should display an error message via an Exception
16. Print out the current balance (which should still be $0)

• Start by writing the CreditAccount class with only the accountBalance field, a toString() method that outputs the balance, and a main() method that instantiates a new instance of the CreditAccount class and outputs the result of calling the toString() method.  Compile and test to make sure that this simple version works.
• Gradually build up the functionality of the CreditAccount class, adding each field and method in turn, testing thoroughly that your class works at each step.  Do this very gradually, breaking the development of the CreditAccount class into about 10 steps, just as I did for you in assignment 1.
  
• It is often a handy trick to write a main() method for every class that tests the class thoroughly, as we've done in this assignment.  This is very useful for diagnostic purposes, and will be essential when we start developing larger programs.
  

Be certain that your CreditAccount.java file contains proper header comments that include your name.

Place your CreditAccount.java file and compiled CreditAccount.class file into a directory entitled LastnameFirstname-Assignment2.  Compress this folder as a zip or tar file, and submit it via Dropbox, as detailed in the assignment submission instructions.