OOP Dalam Mesin ATM

Pada kesempatan kali ini, saya akan membagikan ilmu mengenai cara membuat Mesin ATM sederhana menggunakan Java, dengan panduan dari buku “Java How To Program” karya Paul Deitel dan Harvey Deitel.

Untuk class diagram dengan attr dan operations, bisa digambarkan sebagai berikut.

Langsung ke bagian source code:

• Class ATM

public class ATM
{
    private boolean userAuthenticated;
    private int currentAccountNumber;
    private Screen screen;
    private Keypad keypad;
    private CashDispenser cashDispenser;
    private DepositSlot depositSlot;
    private BankDatabase bankDatabase;
   
    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;
   
    public ATM()
    {
        userAuthenticated = false;
        currentAccountNumber = 0;
        screen = new Screen();
        keypad = new Keypad();
        cashDispenser = new CashDispenser();
        depositSlot = new DepositSlot();
        bankDatabase = new BankDatabase();
       
    }
   
    public void run()
    {
        while ( true )
        {
            while ( !userAuthenticated )
            {
                screen.displayMessageLine( "\nWelcome!" );
                authenticateUser();
            }
           
            performTransactions();
            userAuthenticated = false;
            currentAccountNumber = 0;
            screen.displayMessageLine( "\nThank you! Goodbye!" );
        }
    }
   
    private void authenticateUser()
    {
        screen.displayMessage( "\nPlease enter your account number: " );
        int accountNumber = keypad.getInput();
        screen.displayMessage( "\nEnter your PIN: " );
        int pin = keypad.getInput();
       
        userAuthenticated =
           bankDatabase.authenticateUser( accountNumber, pin );
       
        if ( userAuthenticated )
        {
            currentAccountNumber = accountNumber;
        }
        else
        {
            screen.displayMessageLine("Invalid account number or PIN. Please try again." );
        }
    }
   
    private void performTransactions()
    {
        Transaction currentTransaction = null;
        boolean userExited = false;
       
        while ( !userExited )
        {
            int mainMenuSelection = displayMainMenu();
           
            switch ( mainMenuSelection )
            {
                case BALANCE_INQUIRY:
                case WITHDRAWAL:
                case DEPOSIT:
                     currentTransaction = createTransaction( mainMenuSelection );
               
                     currentTransaction.execute();
                     break;
                case EXIT:
                    screen.displayMessageLine( "\nExiting the system..." );
                    userExited = true;
                    break;
                default:
                    screen.displayMessageLine("\nYou did not enter a valid selection. Try again." );
                    break;
            }
        }
    }
   
    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();
    }
   
    private Transaction createTransaction( int type )
    {
        Transaction temp = null;
       
        switch ( type )
        {
            case BALANCE_INQUIRY:
                temp = new BalanceInquiry( currentAccountNumber, screen, bankDatabase );
                break;
            case WITHDRAWAL:
                temp = new Withdrawal( currentAccountNumber, screen, bankDatabase, keypad, cashDispenser );
                break;
            case DEPOSIT:
                temp = new Deposit( currentAccountNumber, screen, bankDatabase, keypad, depositSlot );
                break;
        }
       
        return temp;
    }
}

• Class Screen

public class Screen
{
    public void displayMessage( String message )
    {
        System.out.print( message );
    }
   
    public void displayMessageLine( String message )
    {
        System.out.println( message );
    }
   
    public void displayDollarAmount( double amount )
    {
        System.out.printf( "$%,.2f", amount );
    }
   
}