CS 3291 (Java with Internet Applications):
Homework #2

Assigned:

September 10, 1999.

Due:

September 24, 1999, class time.

Credit:

20 points.

Objective:

Write a program that defines and uses a variety of classes.

General description:

You are to write a program that simulates some of the operation of a bank. For this program, you can regard a bank as a collection of accounts. For each account, the bank records an account number (integer), a PIN (integer), a name (string), a balance (integer), and a transaction history (more about that shortly). This bank is a closed system in that money can be transferred from one account to another, but not to or from the outside world. We want to record the following types of transactions:

• initial balance, specifying the amount
• outgoing transfers, specifying the amount and the account to which it went
• incoming transfers, specifying the amount and the account from which it came

Since we have not yet discussed Java's GUI features, the program will have a simple CLI, described below. You will have access to an Input class that provides relatively easy-to-use methods for reading from files and standard output, and you already know how to write to standard output.

Instructions:

1. Read about the Input class in Helpful hints section below and look at the sample programs.
2. Read the detailed description of the bank program in the Detailed description section below.
3. Decide what classes (in addition to a Bank class) you want to define.
4. Implement the classes you decide on, and then use them to write a program that behaves as described below. You should end up with a Bank class whose main method behaves as described, and probably some other classes as well. To simplify the grading process, aim to have a single source file called Bank.java. See the Helpful hints section below if you're confused about how to do this.
5. Test the program until you are satisfied that it works.
6. Submit your Java source file, as described in How to submit homework.

Helpful hints:

1. You can use the Input class, defined in Input.java, to do input from a file or from standard input (the terminal, unless redirected). This class, written by a professor at University of Florida for her introductory course, provides some pretty easy-to-use methods for reading numbers and strings from either standard input or a file. See the main method in the Input class, or example programs TestInput.java, TestFileInput.java, and TestInputLoop.java, for examples of using these methods. To make use of this class, copy the source into the directory in which you will be working and compile it. You can assume that when we test your program, we will supply a copy of Input.class, so you do not need to copy code from Input.java into your source.
2. You may find some of Java's core classes -- the ones we've discussed in class so far -- helpful. (If you have not already done so, read about the Vector and Hashtable classes in chapter 9.)
3. You may also find the partial example from February 5's class helpful as an example of (1) object-oriented design for a somewhat similar problem and (2) defining and using more than one class in a single source file. See AddrBook.java.

Detailed description:

• The Bank program is to be invoked with one command-line argument specifying the name of a file containing data to initialize a bank object -- i.e., to set up the collection of accounts. For each account to be set up, the file provides the following information:
  • account number and PIN (integers)
  • first, middle, and last names (strings)
  • initial balance (integer)
  Here is an example of such a file:

  1234 4321 The Little Company 100000
  2345 5432 One Good Employee 2000
  3456 6543 Another Good Employee 4000
  4567 7654 A Helpful Nanny 200
  5678 8765 The Corner Store 20000
  

  The first account set up would have account number 1234, PIN 4321, name "The Little Company", and an initial balance of $100000.

  You can assume that the file has the correct format -- numbers where there are supposed to numbers, strings where there are supposed to be strings. Your program should, however, be prepared to accept a file of arbitrary length -- four lines as in the above, or ten, or a hundred.

• Once the program has processed its input file, it begins an interactive dialog, reading from standard input and writing to standard output, continuing until end-of-file is reached on standard input (i.e., if the program is running with standard input coming from a terminal, it runs until the user presses the end-of-input key (control D for Unix, control Z for DOS). This dialog runs as follows:
  1. Prompt for and read an account number. If the number provided is invalid (no such account), write an error message and return to step 1.
  2. Prompt for and read a PIN. If the number provided is invalid (wrong PIN for the account number), write an error message and return to step 1.
  3. Display the name in the form "Welcome, The Name Here".
  4. Prompt for and read a letter indicating the type of action requested: "B" for balance inquiry, "L" for last transaction, "H" for transaction history, "T" for funds transfer. If the response isn't one of those options, write an error message and return to step 1.
  5. Process request as follows:
     • For "B", display the balance.
     • For "L", display the last (i.e., most recent) transaction.
     • For "H", display all transactions in reverse order (i.e, most recent first, then next most recent, etc.).
     • For "T", proceed thus:
       • Prompt for and read the account number to transfer funds to (the "to" account, as opposed to the "current" account -- the one for which the user has already provided an accout number and PIN). If number provided is invalid (no such account), write an error message and return to step 1.
       • Prompt for and read the amount to transfer. If the amount is invalid (less than 0 or greater than the balance of the current account), write an error message and return to step 1.
       • Redisplay the "to" account and amount and prompt for and read confirmation ("Y" to confirm, "N" to cancel). If the response is not "Y", write a message indicating the that request was cancelled and return to step 1.
       • Transfer the requested amount -- i.e., deduct it from the current account's balance and add it to the "to" account's balance. Note that the transfer should be recorded in the transaction histories of both accounts.
  6. Return to step 1. (Continue until EOF is reached, which if you are using the provided Input class will be signalled by an exception. See the TestInputLoop example program.)
  You need not check for errors other than those described above -- e.g., you may assume that the account number as entered is numeric.

  Some observations about this interface:

  • It's intended to model the interface between "the bank" (in the form of, say, an automated bank-by-phone system, or an ATM) and a sequence of users, each performing one or more transactions (balance inquiry, funds transfer, etc.). It's not particularly friendly, since if a user makes a mistake, he/she must start the whole process over. However, it allows a user to bail out at any point, leaving "the bank" ready to respond to a new user. (Also, it's intended to be easier to implement than a commercial-quality user interface, since the user interface isn't the point of this assignment.)
  • It requires users to supply PINs for accounts they want to inquire about or remove money from, but not for those they want to put money into. This allows, e.g., a company to use the system to pay its employees without knowing their PINs.
  Here is a sample dialog that might follow initialization with the previously-shown input file, with user responses in boldface. Please use the format and wording of the prompts, error messages, etc. in this example.

  Enter account number
  1111
  Invalid account number
  Enter account number
  1234
  Enter PIN
  2222
  Invalid PIN
  Enter account number
  4321
  Invalid account number
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  oops
  Invalid request type
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  B
  Balance: $100000
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  L
  Last transaction: initial balance in the amount of $100000
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  H
  Transaction history:
  initial balance in the amount of $100000
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  T
  Enter account number to transfer to
  1111
  Invalid account number
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  T
  Enter account number to transfer to
  2345
  Enter amount to transfer
  1000000
  Invalid amount
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  T
  Enter account number to transfer to
  2345
  Enter amount to transfer
  2000
  Confirm transfer of $2000 to account 2345: Enter Y to confirm, N to cancel
  N
  Request cancelled
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  T
  Enter account number to transfer to
  2345
  Enter amount to transfer
  2000
  Confirm transfer of $2000 to account 2345: Enter Y to confirm, N to cancel
  Y
  Funds transferred
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  T
  Enter account number to transfer to
  3456
  Enter amount to transfer
  1000
  Confirm transfer of $1000 to account 3456: Enter Y to confirm, N to cancel
  Y
  Funds transferred
  Enter account number
  1234
  Enter PIN
  4321
  Welcome, The Little Company
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  H
  Transaction history:
  transfer to account 3456 in the amount of $1000
  transfer to account 2345 in the amount of $2000
  initial balance in the amount of $100000
  Enter account number
  3456
  Enter PIN
  6543
  Welcome, Another Good Employee
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  T
  Enter account number to transfer to
  4567
  Enter amount to transfer
  400
  Confirm transfer of $400 to account 4567: Enter Y to confirm, N to cancel
  Y
  Funds transferred
  Enter account number
  3456
  Enter PIN
  6543
  Welcome, Another Good Employee
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  B
  Balance: $4600
  Enter account number
  3456
  Enter PIN
  6543
  Welcome, Another Good Employee
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  H
  Transaction history:
  transfer to account 4567 in the amount of $400
  transfer from account 1234 in the amount of $1000
  initial balance in the amount of $4000
  Enter account number
  3456
  Enter PIN
  6543
  Welcome, Another Good Employee
  Enter B for balance inquiry, L for last transaction, H for transaction history, T for funds transfer
  L
  Last transaction: transfer to account 4567 in the amount of $400
  

Grading:

This homework is worth 20 points:

• 16 points for correctness. I will execute your program on a standard suite of test inputs.
• 4 points for style. See Programming style for notes on what I consider good programming style. I will try to evaluate (in a tolerant way, for this assignment) and comment on your decisions about what classes to implement and how to put them together.