ATM Case Study

Author: phongus

13 ATM Case Study/.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>13 ATM Case Study</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

13 ATM Case Study/src/ATM.java

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+//	ATM.java
+//	Represents an automated teller machine
+
+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 authenticate
+			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.diplayMessage("\nPlease enter your account number: ");
+		int accountNumber = keypad.getInput();	//	input account number
+		screen.diplayMessage("\nEnter your PIN: ");	//	prompt for PIN
+		int pin = keypad.getInput(); //	input PIN
+		
+		//	set userAuthentigated to boolean value returned by the 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 - View my balance");
+		screen.displayMessageLine("4 - Withdraw cash");
+		screen.displayMessageLine("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
+
+

13 ATM Case Study/src/Account.java

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+//	Account.java
+//	Represents a bank account
+
+public class Account 
+{
+	private int accountNumber;	//	
+	private int pin;	//	PIN for authentication
+	private double	availableBalance;	//	funds available for withdrawal
+	private double totalBalance;	//	funds available + pending deposits
+	
+	//	Account constructor initializes attributes
+	public Account(int theAccountNumber, int thePIN,
+			double theAvailableBalance, double theTotalBalance)
+	{
+		accountNumber = theAccountNumber;
+		pin = thePIN;
+		availableBalance = theAvailableBalance;
+		totalBalance = theTotalBalance;
+	}	//	end Account constructor
+	
+	//	determines whether a user-specific PIN matches PIN in Account
+	public boolean validatePIN(int userPIN)
+	{
+		if(userPIN == pin)
+			return true;
+		else
+			return false;
+	}	//	end method validatePIN
+	
+	//	return available balance
+	public double getAvailableBalance()
+	{
+		return availableBalance;
+	}	//	end getAvailableBalance
+	
+	//	returns the total balance
+	public double getTotalBalance()
+	{
+		return totalBalance;
+	}	//	end method getTotalBalance
+	
+	//	credits an amount to the account
+	public void credit(double amount)
+	{
+		totalBalance += amount;	//	add to total balance	
+	}	//	end method credit
+	
+	//	debits an amount from the account
+	public void debit(double amount)
+	{
+		availableBalance -= amount;	//	subtract from available balance
+		totalBalance -=	amount;	//	subtract from total balance
+	}	//	end method debit
+	
+	//	returns account number
+	public int getAccountNumber()
+	{
+		return accountNumber;
+	}	//	end method getAccountNumber
+}	//	end class Account

13 ATM Case Study/src/BankDatabase.java

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+//	BankDatabase.java
+//	Represents the bank account information database
+
+public class BankDatabase 
+{
+	private Account[] accounts;	//	array of Accounts
+	
+	//	no-argument BankDatabase constructor initializes accounts
+	public BankDatabase()
+	{
+		accounts = new Account[2];	//	just 2 accounts for testing
+		accounts[0] = new Account(12345, 54321, 1000.0, 1200.0);
+		accounts[1] = new Account(98765, 56789, 200.0, 200.0);
+	}	//	end no-argumnent BankDatabase constructor
+	
+	//	retrieve Account object containing specified account number
+	private Account getAccount(int accountNumber)
+	{
+		//	loop through accounts searching for matching account number
+		for (Account currentAccount : accounts)
+		{
+			//	return current account if match found
+			if (currentAccount.getAccountNumber() == accountNumber)
+				return currentAccount;
+		//	end for
+		}
+	
+	return null;	//	if no matching account was found, return null
+	}	//	end method getAccount
+
+	//	determine whether user-specified account number and PIN match
+	//	those of an account in the database
+	public boolean authenticateUser(int userAccountNumber, int userPIN)
+	{
+		//	attempt to retrieve the account with the account number
+		Account userAccount = getAccount(userAccountNumber);
+	
+		//	if account exists, return result of Account method validatePIN
+		if(userAccount != null)
+			return userAccount.validatePIN(userPIN);
+		else
+			return false;	//	account number not found, so return false
+	}	//	end method authenticateUser
+
+	//	return available balance of Account with specified account number
+	public double getAvailableBalance(int userAccountNumber)
+	{
+		return getAccount(userAccountNumber).getAvailableBalance();
+	}	//	end method getAvailableBalance
+
+	//	return total balance of Account with specified account number
+	public double getTotalBalance(int userAccountNumber)
+	{
+		return getAccount(userAccountNumber).getTotalBalance();
+	}	//	end method getTotalBalance
+
+	//	credit an amount to Account with specified account number
+	public void credit(int userAccountNumber, double amount)
+	{
+		getAccount(userAccountNumber).credit(amount);
+	}	//	end method credit
+
+	//	debit an amount from Account with specified account number
+	public void debit(int userAccountNumber, double amount)
+	{
+		getAccount(userAccountNumber).debit(amount);
+	}
+
+}

13 ATM Case Study/src/CashDispenser.java

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+//	CashDispenser.java
+//	Represents the cash dispenser of the ATM
+
+public class CashDispenser 
+{
+	//	the default initial number of bills in the cash dispenser
+	private final static int INITIAL_COUNT = 500;
+	private int count;	//	number of $20 bills remaining.
+	
+	//	no-argument CashDispenser 
+	public CashDispenser()
+	{
+		count = INITIAL_COUNT;	//	set count attribute to default
+	}	//	end CashDispenser constructor
+	
+	//	simulates dispensing of specified amount of cash
+	public void dispenseCash(int amount)
+	{
+		int billsRequired = amount / 20;	//	number of $20 bills required
+		count -= billsRequired;	//	update the count of bills
+	}	//	end method dispenseCash
+	
+	//	indicates whether cash dispenser can dispense desired amount
+	public boolean isSufficientCashAvailable(int amount)
+	{
+		int billsRequired = amount / 20;	//	number of $20 bills required
+		
+		if (count >= billsRequired)
+			return true;	//	enough bills available
+		else
+			return false;	//	not enough bills available
+	}	//	end method isSufficientCashAvailable
+}	//	end class CashDispenser

13 ATM Case Study/src/DepositSlot.java

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+//	DepositSlot.java
+//	Represents the deposit slot of the ATM
+
+public class DepositSlot 
+{
+	//	indicates whether envelope was recieved (always returns true,
+	//	because this is only a software simulation of a real deposit slot)
+	public boolean isEnvelopeRecieved()
+	{
+		return true;	//	deposit envelope was received
+	}	//	end method isEvelopeRecieved
+}	//	end class DepositSlot

13 ATM Case Study/src/Keypad.java

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+//	Keypad.java
+//	Represents the keypad of the ATM
+import java.util.Scanner;	//	program uses Scanner to obtain user input
+
+public class Keypad 
+{
+	private Scanner input;	//	reads data from the command line
+	
+	//	no-argument constructor initializes the Scanner
+	public Keypad()
+	{
+		input = new Scanner(System.in);
+	}	//	end no-argument Keypad constructor
+	
+	//	return an integer value entered by user
+	public int getInput()
+	{
+		return input.nextInt();
+	}	//	end method getInput
+}	//	end class Keypad

13 ATM Case Study/src/Screen.java

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+//	Screen.java
+//	Represents the screen of the ATM
+
+public class Screen 
+{
+	//	display a message without a carriage return
+	public void diplayMessage(String message)
+	{
+		System.out.print(message);
+	}	//	end method displayMessage
+	
+	//	display a message with a carriage return
+	public void displayMessageLine(String message)
+	{
+		System.out.println(message);
+	}	//	end method displayMessageLine
+	
+	//	display a dollar amount
+	public void displayDollarAmount(double amount)
+	{
+		System.out.printf("$%,.2f", amount);
+	}	//	end method displayDollarAmount
+}	//	end class Screen