CMSC 206 (Introduction to Computing)

Assignment#1

Part A Due:  September 07, 2011 11:59:59pm
Part B Due:  September 19, 2011 11:59:59pm
Part B Due:  September 21, 2011 11:59:59pm

The goal of this assignment is to develop your ability to do object-oriented programming, focusing specifically on inheritance. 

To begin, download these two files:  Assignment1Skeleton.java and CS206Assignment1.jar.  The first (java) file is skeleton version of the program; start with this file and fill in the parts marked as "FIXME" to complete the assignment.  The second (jar) file is a completed version of the assignment that you can study.  To run this completed program, use the command java -jar CS206Assignment1.jar

You will write a program that allows a user to repeatedly create new credit accounts from three possible types: a standard account, a gold account, or a last-chance account.

• A standard credit account has an annual interest rate of 15%, and an upper limit of $4,000.
• A gold account has an annual interest rate of 10% and an upper limit of $100,000. In addition, gold card holders earn 2% cashback on every purchase.
  
• A last-chance account is for people with a bad credit history. The annual interest rate is 25% and there is a $1,000 charge limit. However, a last chance card holder can get a better deal by consistently paying off the entire balance. If a last chance card holder pays off the balance three times in a row, then their interest rate drops to 20% and their limit increases to $1,500.  However, if they miss a payment (noted by a payment of 0), their interest rate will increase to 27%.
  

Starting with the skeleton file provided above, you will modify the two parts marked as "FIXME" to complete the assignment. 

• Complete the userMenu() function to properly display the options for interacting with a single account, following the menu format given below in the example trace.  The skeleton file already provides examples of several menus that you can model to complete this task.  Your function should use proper error checking on the inputs, especially when prompting the user for charge/payment amounts.  Experiment with the demo program given in the jar file above, trying different inputs to see how the program behaves.
• Implement an abstract 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.
• Accessors and setters for all private variables needed outside the class with appropriate public/protected access levels.
• A toString() function that outputs a textual description of the account, which is used in the provided code.
• The following two abstract functions:
• 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.
  
• void makePayment(double amount) which reduces the balance by the specified amount.  You can assume that this function is called only once at the end of each month, and so it 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, the interest would be assessed against $200.  The interest rates listed above are annual rates, so you should divide them by 12 to get the monthly rate used to compute the interest in the makePayment() function.
• Implement classes for each of the three account types that extend the CreditAccount and implement the appropriate behavior for each type of account.  These subclasses should reuse as much as possible from the base CreditAccount class.  If functionality is shared between all three account types, then it should be included in the CreditAccount class (i.e., don't implement the same thing three times in the subclasses, implement it once in the CreditAccount class).
  
• Be sure to do error checking on the inputs.  Negative payments and charges are not allowed, although the user can carry a minimum balance.
• Although most credit cards usually have a minimum payment due, we will ignore this aspect for this assignment.
• 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.
  
• All of the provided code can be used as-is, except where noted explicitly in the file.  In other words, you should not need to change anything in main, in any of the menu functions other than userMenu(), and the utility functions.
• While you are free to be creative with some of the messages, you program must follow the same menu structure, the ordering of the options, and the effects of each button press.  In other words, if I close my eyes at the main menu and then choose option 2, enter account number 0, then option 2, and then type 300, your program should do the exact same thing (charge the account $300) as the sample program.  You can improve the look of the menu system, the wording of the messages, the formatting of the amounts (for example, make all dollar amounts be outputted to two decimal places), and the output details; just don't change the program functionality.  If you do wish to add new features, you can add additional items to the end of any menu.
  

For part A of this assignment, you should complete the userMenu() method to make a functioning menu system.  However, to simply things, instead of actually acting on the accounts, simply print out the action the program would have taken if it were complete.  You should not need to modify any code outside of the userMenu() function to accomplish this.

This part is only to have you do some basic coding, compile the program, and submit it.  Don't worry about doing it wrong.  So long as you have some form of a functional user menu, you will get full credit for completing this part.  However, here is an example trace to give you an idea of what I'm looking for:


This second part is simply to complete the rest of the assignment, as described in the Introduction and Program Requirements listed above.  Here's an example trace of the program running once Part B is complete.

• Start by compiling and running the provided java file.  It currently skips over the user menu, which you'll need to implement in Part A.
• Also experiment with the provided demo in the jar file, noting how the menus work, how the program functions, and how input errors are handled.
• Read over the java file in detail several times to ensure that you know how each line in the file works and what it does.
  
• Next, implement the user menu as described in the requirements for Part A above.
• Implement the abstract CreditAccount class and then create the class for the standard card.  Get the standard card class working correctly before moving on to the two other account types.
• Develop the CreditAccount and Standard account class incrementally, slowing adding in functionality and then also integrating that functionality into the user menu.  Do not try to build all functionality at once.  Build one part, get it working, and then move on to the next.
  
• Use good object-oriented design throughout the assignment, focusing especially on code re-use.  Always try to place common functionality in the superclass, keeping the subclasses as minimal as possible.
  

Copy all your .java files for the project into a folder called Assignment01-PartA or Assignment01-PartB in dropbox before the deadlines.  I will provide more detailed descriptions on submitting files via dropbox shortly.

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Acknowledgement:  This assignment was adapted from a lab assignment and materials provided by Andrew Danner.  All code was written by Eric Eaton.