ATM.java

public class ATM
{
     private boolean userAuthenticated; // whether user is authenticated
     private int currentAccountNumber; // current user's account number
     private Screen screen; // ATM's screen
     private Keypad keypad; // ATM's keypad
     private CashDispenser cashDispenser; // ATM's cash dispenser
     private DepositSlot depositSlot; // ATM's deposit slot
     private BankDatabase bankDatabase; // account information database

     // constants corresponding to main menu options
     private static final int BALANCE_INQUIRY = 1;
     private static final int WITHDRAWAL = 2;
     private static final int DEPOSIT = 3;
     private static final int EXIT = 4;

     // no-argument ATM constructor initializes instance variables
     public ATM()
     {
         userAuthenticated = false; // user is not authenticated to start
         currentAccountNumber = 0; // no current account number to start
         screen = new Screen(); // create screen
         keypad = new Keypad(); // create keypad
         cashDispenser = new CashDispenser(); // create cash dispenser
         depositSlot = new DepositSlot(); // create deposit slot
         bankDatabase = new BankDatabase(); // create acct info database
     } // end no-argument ATM constructor

     // start ATM
     public void run()
     {
         // welcome and authenticate user; perform transactions
         while ( true )
         {
             // loop while user is not yet authenticated
             while ( !userAuthenticated )
             {
                screen.displayMessageLine( "\nWelcome!" );
                authenticateUser(); // authenticate user
             } // end while
             performTransactions(); // user is now authenticated
             userAuthenticated = false; // reset before next ATM session
             currentAccountNumber = 0; // reset before next ATM session
             screen.displayMessageLine( "\nThank you! Goodbye!" );
         } // end while
     } // end method run

     // attempts to authenticate user against database
     private void authenticateUser()
     {
         screen.displayMessage( "\nPlease enter your account number: " );
         int accountNumber = keypad.getInput(); // input account number
         screen.displayMessage( "\nEnter your PIN: " ); // prompt for PIN
         int pin = keypad.getInput(); // input PIN

         // set userAuthenticated to boolean value returned by database
         userAuthenticated =
         bankDatabase.authenticateUser( accountNumber, pin );

         // check whether authentication succeeded
         if ( userAuthenticated )
         {
             currentAccountNumber = accountNumber; // save user's account #
         } // end if
         else
         screen.displayMessageLine("Invalid account number or PIN. Please try again.");
     } // end method authenticateUser

     // display the main menu and perform transactions
     private void performTransactions()
     {
         // local variable to store transaction currently being processed
         Transaction currentTransaction = null;
         boolean userExited = false; // user has not chosen to exit

         // loop while user has not chosen option to exit system
         while ( !userExited )
         {
             // show main menu and get user selection
             int mainMenuSelection = displayMainMenu();

             // decide how to proceed based on user's menu selection
             switch ( mainMenuSelection )
             {
                 // user chose to perform one of three transaction types
                 case BALANCE_INQUIRY:
                 case WITHDRAWAL:
                 case DEPOSIT:

                 // initialize as new object of chosen type
                 currentTransaction =
                 createTransaction( mainMenuSelection );

                 currentTransaction.execute(); // execute transaction
                 break;

                 case EXIT: // user chose to terminate session
                 screen.displayMessageLine( "\nExiting the system..." );
                 userExited = true; // this ATM session should end
                 break;

                 default: // user did not enter an integer from 1-4
                 screen.displayMessageLine("\nYou did not enter a valid selection. Try again.");
                 break;
             } // end switch
         } // end while
     } // end method performTransactions

     // display the main menu and return an input selection
     private int displayMainMenu()
     {
         screen.displayMessageLine( "\nMain menu:" );
         screen.displayMessageLine( "1 - View my balance" );
         screen.displayMessageLine( "2 - Withdraw cash" );
         screen.displayMessageLine( "3 - Deposit funds" );
         screen.displayMessageLine( "4 - Exit\n" );
         screen.displayMessage( "Enter a choice: " );
         return keypad.getInput(); // return user's selection
     } // end method displayMainMenu

     // return object of specified Transaction subclass
     private Transaction createTransaction( int type )
     {
         Transaction temp = null; // temporary Transaction variable

         // determine which type of Transaction to create
         switch ( type )
         {
             case BALANCE_INQUIRY: // create new BalanceInquiry transaction
             temp = new BalanceInquiry(
             currentAccountNumber, screen, bankDatabase );
             break;

             case WITHDRAWAL: // create new Withdrawal transaction
             temp = new Withdrawal( currentAccountNumber, screen,
             bankDatabase, keypad, cashDispenser );
             break;

             case DEPOSIT: // create new Deposit transaction
             temp = new Deposit( currentAccountNumber, screen,
             bankDatabase, keypad, depositSlot );
             break;
         } // end switch

         return temp; // return the newly created object
     } // end method createTransaction
} // end class ATM