Some guidance with a Bank System

[Trish Murphy]

Hey, New to Java and this forum! I have a school project that i'm having difficulty with understanding. we were allowed choose whatever we wanted I chose a bank and i'm regretting it now!!! Basically I wanted a Customer Class to hold all the personal details , an Account Class, a transaction class and a main driver code with the gui to display everything. The first thing i'm stuck with is I don't really understand the "Has a " relationship. Like the customer has Accounts but how do I actually link them?? I'm going to post my code so far but its all over the place and very messy, i'm just very confussed at the moment!!

this is the Account Class so far

import java.io.*;
/**
 * @(#)BankAccount.java
 *
 *
 * @author
 * @version 1.00 2009/11/17
 */


public class BankAccount{

	private double balance;
	private int accountNumber;
	private String lastName;
	Customer customer;

	private static int nextAccId = 1001;

	/** no-argument constructor
	 */

	public BankAccount(Customer customer) {
		this.accountNumber = nextAccId++;
		this.customer = customer;
		balance = 0;



	}
	public String getLastName()
	{	return lastName;

	}

	public int getAccountNumber(){
		return(accountNumber);
	}

    public double getBalance(){
    	return(balance);
    }



	public void setAccountNumber (int accNo) {
				accountNumber = accNo;
	}
	public void setBalance (double bal) {
				balance = bal;
	}

		public static int getNextAccId() {
		return nextAccId;
	}

	public static void setNextAccId(int nextAccId){
		BankAccount.nextAccId=nextAccId;
	}


  public String toString()
	{
	return "Account number "
              + accountNumber + " belonging to "
              + customer.getLname() + "Customer Id"
              + customer.getCustid() + 	" has a balance of £" + balance;
	}



public String credit(double anAmount)
{
balance +=anAmount;
return " Account number " + accountNumber + " has been credited with £"+ anAmount;
}

public boolean canDebit(double anAmount)
{
return anAmount<=balance;
}


public String debit(double anAmount)
{
if(this.canDebit(anAmount))
   {
    balance -= anAmount;
     return "£" +  anAmount +
" has been debited from Acount number " + 	accountNumber;
	}
else
	{
     	return "Account number " + 	accountNumber  +
	" has insufficient funds to debit £" 	+anAmount;
	}

}

}

This is the Customer Class so far

import java.io.*;

public class Customer implements Serializable{
 	String fname, lname;
	private int age , custid;
	private char gender;

	private static int nextId = 1;
	private BankAccount myBankAccount;


	/** no-argument constructor
	 */
	public Customer() {
				setCustid(0);
				setFname("unassigned");
				setLname("unassigned");
				setAge(0);
				setGender('u');

	}
	public Customer(String fname){
		setFname(fname);
		setCustid(nextId);
		nextId++;
	}

	// full-args constructor,

	public Customer(String fname, String lname, int age, char gender) {

				setCustid(nextId);
				setFname(fname);
				setLname(lname);
				setAge(age);
				setGender(gender);

				nextId++;
	}
 public Customer(int custId, String fname, String lname, int age, char gender) {

				setCustid(custId);
				setFname(fname);
				setLname(lname);
				setAge(age);
				setGender(gender);


	}

	// 'accessor'/'getter' methods to return a copy of an attribute
	public int getCustid() {
		return custid;
	}
	public String getFname() {
		return fname;
	}
	public String getLname() {
		return lname;
	}
	public int getAge() {
		return age;
	}

	public char getGender() {
		return gender;
	}



	// 'mutator'/'setter methods to change the value of an attribute

	public void setCustid (int cstid) {
				custid = cstid;
	}
	public void setFname (String fnm) {
				fname = fnm;
	}
	public void setLname (String lnm) {
				lname = lnm;
	}

	public void setAge (int ag) {
				age = ag;
	}


	public void setGender(char gndr) {
				gender = gndr;
	}

	// 'constructor' methods



	public String toString() {
				return "Customer: " + getCustid() + " " + getFname() + " " + getLname() + " " + getAge() + " " + getGender();
	}
	public static int getNextId() {
		return nextId;
	}

	public static void setNextId(int nextId){
		Customer.nextId=nextId;
	}
}

This is the Transaction Class (Haven't figured out where i am going with that yet)

import java.io.*;
import java.util.*;  // for ArrayList
/**
 * @(#)Transaction.java
 *
 *
 * @author
 * @version 1.00 2012/3/29
 */


public class Transaction{
	Customer customer;
	BankAccount bankAccount;
	double amount;
	String date;

	private boolean successfulTransaction = false;
	public static final int LODGEMENT = 1;
	public static final int WITHDRAWAL = 2;
	public static final int BALANCEENQ = 3;



    public Transaction() {
    	customer = new Customer();
    	bankAccount = new BankAccount();
    	date = "no date";
    }

 	public Transaction(Customer customer, BankAccount bankAccount) {
    	setCustomer = (customer);
    	setBankAccount = (bankAccount);
    	date = "no date";
    }
	public Transaction(Customer customer, BankAccount bankAccount, String date) {
    	setCustomer = (customer);
   	setBankAccount = (bankAccount);
   	setDate = (date);
    }
 	public void setCustomer(Customer customer){
    	this.customer = customer;
    }

    public void setBankAccount(BankAccount bankAccount){
    	this.bankAccount = bankAccount;
    }

    public void setDate(String date){
    	this.date = date;
    }

    public void setAmount(double amount){
    	this.amount = amount;
    }

    public String toString() {
    	return "Customer: " + customer + "\nAccount No: " + bankAccount +
    		"\nAmount: " + amount + "\nDate taken out: " + getDate();
    }

    public String getDate() { return date;}
    public double getAmount() { return amount;}
    public Customer getCustomer() { return customer;}
    public BankAccount getbankAccount() { return bankAccount;}

}

And the Driver Code

import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.io.*;

public class MainMenuScreen extends JFrame implements ActionListener{

    JMenu customerMenu, accountMenu, transactionMenu, fileMenu;
    ArrayList<Customer> custList;
    ArrayList<BankAccount> accountList;
    ArrayList<Transaction> transactionList;
    JTextArea area;

	public static void main(String args[]){
		 JOptionPane.showMessageDialog(null, "Welcome to my Bank!" );
		MainMenuScreen win = new MainMenuScreen();
		win.setVisible(true);
	}

	public MainMenuScreen(){
			setTitle("My Bank");
			setSize(600,600);
			setLocation(250,200);
			// exit as the default closing operation
			// see the other possibilities in JFrame class
			setDefaultCloseOperation(EXIT_ON_CLOSE);
			JMenuBar bar = new JMenuBar();
			setJMenuBar(bar);
			createFileMenu();
			bar.add(fileMenu);
			createCustomerMenu();
			bar.add(customerMenu);
			createAccountMenu();
			bar.add(accountMenu);
			createTransactionMenu();
			bar.add(transactionMenu);
			custList = new ArrayList<Customer>();
			accountList = new ArrayList<BankAccount>();
			transactionList = new ArrayList<Transaction>();
			area = new JTextArea();

			createUserInterface();
	} // end constructor

	public void saveData() {
		try{
			ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("banktrans.data"));
			os.writeObject(custList);
			os.writeObject(accountList);
			os.writeObject(transactionList);
			os.close();
				JOptionPane.showMessageDialog (null,"Data Saved");
		}
		catch (IOException e){
			JOptionPane.showMessageDialog (null,"Save Aborted");
			e.printStackTrace();
		}
	}

	public void loadData() {
	try{
			ObjectInputStream is = new ObjectInputStream(new FileInputStream("banktrans.data"));
			custList = (ArrayList<Customer>) is.readObject();
			accountList = (ArrayList<BankAccount>) is.readObject();
			transactionList = (ArrayList<Transaction>) is.readObject();
			is.close();
			JOptionPane.showMessageDialog (null,"Data loaded");
		}
		catch (Exception e){
			JOptionPane.showMessageDialog (null,"Load Aborted");
			e.printStackTrace();
		}
	}

	public void addCustomer(){
		String fname = JOptionPane.showInputDialog(null, "Enter Customers First Name");

		custList.add(new Customer(fname));

		String lname = JOptionPane.showInputDialog(null, "Enter Customers  Surname");

		custList.add(new Customer(lname));

		//int age = JOptionPane.showInputDialog(null, "Enter Customers age");

	//	custList.add(new Customer(age));

		//char gender = JOptionPane.showInputDialog(null, "Enter Customers gender");
		//custList.add(new Customer(gender));
	}


	public void displayCustomers(){
		area.setText("Customer List\n");
		for (Customer c : custList)
             area.append(c.toString() + "\n");
             JOptionPane.showMessageDialog(null,area);
	}
	public void addAccount() {
		String AccNo = JOptionPane.showInputDialog(null,"Account No: ");




	    }


	public void displayAccounts() {
		area.setText("Account List\n");
		for (BankAccount a : accountList)
			area.append(a.toString() + "\n");
		JOptionPane.showMessageDialog(null,area);
	}

	public void Transaction(){

		int cusId = Integer.parseInt(JOptionPane.showInputDialog("Enter a customer number " +
			" between 1 and " + custList.size()));

		int accountId = Integer.parseInt(JOptionPane.showInputDialog("Pick an account number " +
			" between 1 and " + accountList.size()));


		Transaction transaction = new Transaction(custList.get(cusId - 1), accountList.get(accountId - 1));
		accountList.get(accountId-1).lodgement();
		Transaction.setAmount(0.00);
		Transaction.setDate("Thursday");

		transactionList.add(transaction);

	}
	public void displayTransactions(){

		area.setText("Transaction List\n");
		for (Transaction t : transactionList){
			area.append(t.toString());
//			if (t.getTransaction() instanceof Lodgement){

			}
		}

	//	JOptionPane.showMessageDialog(null,area);


	public void Withdrawal() {



	}

		public void actionPerformed(ActionEvent c){
			String c = c.getActionCommand();
			if (c.equalsIgnoreCase("Add a customer"))

				addCustomer();
			else if (c.equalsIgnoreCase("Display All Customers")){

				displayCustomers();

		}
		else
			JOptionPane.showMessageDialog(null, "something strange happening");
}

	private void createFileMenu(){
		fileMenu = new JMenu("File");
		JMenuItem item = new JMenuItem("Save All Data");
		item.addActionListener(this);
		fileMenu.add(item);

		item = new JMenuItem("Load All Data");
		item.addActionListener(this);
		fileMenu.add(item);
		fileMenu.addSeparator();

		item = new JMenuItem("Quit");
		item.addActionListener(this);
		fileMenu.add(item);
	}

		private void createAccountMenu(){
		accountMenu = new JMenu("Accounts");
		JMenuItem item = new JMenuItem("Add an Account");
		item.addActionListener(this);
		accountMenu.add(item);

		item = new JMenuItem("Display All Accounts");
		item.addActionListener(this);
		accountMenu.add(item);
	}
	private void createTransactionMenu(){
		transactionMenu = new JMenu("Transactions");
		JMenuItem item = new JMenuItem("Process a Transaction");
		item.addActionListener(this);
		transactionMenu.add(item);

		item = new JMenuItem("Display All Transactions");
		item.addActionListener(this);
		transactionMenu.add(item);

	}


	private void createCustomerMenu(){
		customerMenu = new JMenu("Customer");
		JMenuItem item = new JMenuItem("Add a customer");
		item.addActionListener(this);
		customerMenu.add(item);

		item = new JMenuItem("Display All Customers");
		item.addActionListener(this);
		customerMenu.add(item);
	}





// 	accountList = (ArrayList<BankAccount>)
 private void createUserInterface() {

 	private JPanel inputDetailJPanel;

	 private JLabel NameJLabel;
    private JTextField NameJTextField;
    inputDetailJPanel

	private JLabel AccountnumJLabel;
    private JTextField AccountnumJTextField;

    private JLabel BalanceJLabel;
    private JTextField BalanceJTextField;

     private JLabel LodgeJLabel;
    private JTextField LodgeJTextField;

     private JLabel WithdrawJLabel;
    private JTextField WithdrawJTextField;

     private JButton CreateAccountJButton;

     private JButton DeleteAccountJButton;

    private JButton TransactionJButton;

     private JLabel displayJLabel;
    private JTextArea displayJTextArea;

	inputDetailJPanel.add(area);
      private int BankCount = 0;

      private final int FIRST = 0;
    private final int SECOND = 1;
    private final int THIRD = 2;


        // get content pane for attaching GUI components
       Container contentPane = getContentPane();
   		contentPane.setLayout(null);

 		inputDetailJPanel = new JPanel();
        inputDetailJPanel.setBounds(16, 16, 208, 218);
        inputDetailJPanel.setBorder(new TitledBorder("Input Details"));
        inputDetailJPanel.setLayout(null);
        contentPane.add(inputDetailJPanel);

       NameJLabel = new JLabel();
        NameJLabel.setBounds(8, 32, 90, 23);
        NameJLabel.setText("Name:");
        inputDetailJPanel.add(NameJLabel);


        NameJTextField = new JTextField();
        NameJTextField.setBounds(104, 32, 88, 21);
        NameJTextField.setHorizontalAlignment(JTextField.RIGHT);
        inputDetailJPanel.add(NameJTextField);



       AccountnumJLabel = new JLabel();
        AccountnumJLabel.setBounds(8, 56, 100, 23);
        AccountnumJLabel.setText("Account Number:");
        inputDetailJPanel.add(AccountnumJLabel);


       AccountnumJTextField = new JTextField();
        AccountnumJTextField.setBounds(112, 56, 80, 21);
        AccountnumJTextField.setHorizontalAlignment(JTextField.RIGHT);
        inputDetailJPanel.add(AccountnumJTextField);


        BalanceJLabel = new JLabel();
        BalanceJLabel.setBounds(8, 80, 60, 23);
        BalanceJLabel.setText("Balance:");
        inputDetailJPanel.add(BalanceJLabel);


        BalanceJTextField = new JTextField();
        BalanceJTextField.setBounds(112, 80, 80, 21);
        BalanceJTextField.setHorizontalAlignment(JTextField.RIGHT);
        inputDetailJPanel.add(BalanceJTextField);


         LodgeJLabel = new JLabel();
        LodgeJLabel.setBounds(8, 104, 80, 23);
        LodgeJLabel.setText("Lodgement:");
        inputDetailJPanel.add(LodgeJLabel);


        LodgeJTextField = new JTextField();
        LodgeJTextField.setBounds(112, 104, 80, 21);
        LodgeJTextField.setHorizontalAlignment(JTextField.RIGHT);
        inputDetailJPanel.add(LodgeJTextField);

        WithdrawJLabel = new JLabel();
        WithdrawJLabel.setBounds(8, 128, 60, 23);
        WithdrawJLabel.setText("Withdraw:");
        inputDetailJPanel.add(WithdrawJLabel);



        WithdrawJTextField = new JTextField();
        WithdrawJTextField.setBounds(112, 128, 80, 21);
        WithdrawJTextField.setHorizontalAlignment(JTextField.RIGHT);
        inputDetailJPanel.add(WithdrawJTextField);


         CreateAccountJButton = new JButton();
        CreateAccountJButton.setBounds(112, 152, 80, 24);
        CreateAccountJButton.setText("Create");
        inputDetailJPanel.add(CreateAccountJButton);
        CreateAccountJButton.addActionListener(

        new ActionListener() {
            // event handler called when CreateAccountJButton
            // is clicked
            public void actionPerformed(ActionEvent event) {
                CreateAccountJButtonActionPerformed(event);
            }

        }

        ); // end call to addActionListener

        // set up DeleteAccountButton
        DeleteAccountJButton = new JButton();
        DeleteAccountJButton.setBounds(16, 152, 80, 24);
        DeleteAccountJButton.setText("Delete");
        inputDetailJPanel.add(DeleteAccountJButton);
        DeleteAccountJButton.addActionListener(

        new ActionListener() // anonymous inner class
                {
                    // event handler called when DeleteAccountJButton
                    // is clicked
                    public void actionPerformed(ActionEvent event) {
                        DeleteAccountJButtonActionPerformed(event);

                    }

                }

                ); // end call to addActionListener

        // set up TransactionJButton
        TransactionJButton = new JButton();
        TransactionJButton.setBounds(16, 180, 176, 24);
        TransactionJButton.setText("Make Transaction");
        inputDetailJPanel.add(TransactionJButton);
        TransactionJButton.addActionListener(

        new ActionListener() // anonymous inner class
                {
                    // event handler called when TransactionJButton
                    // is clicked
                    public void actionPerformed(ActionEvent event) {
                        TransactionJButtonActionPerformed(event);
                    }

                } // end anonymous inner class

                ); // end call to addActionListener

        // set up displayJLabel
        displayJLabel = new JLabel();
        displayJLabel.setBounds(240, 16, 150, 23);
        displayJLabel.setText("Account Details:");
        contentPane.add(displayJLabel);

        // set up displayJTextArea
        displayJTextArea = new JTextArea();
        displayJTextArea.setBounds(240, 48, 402, 184);
        displayJTextArea.setEditable(false);
        contentPane.add(displayJTextArea);

        // set properties of application's window
        setTitle("Bank Accounts"); // set title bar string
        setSize(670, 308); // set window size
        setVisible(true); // display window

    } // end method createUserInterface

    private void CreateAccountJButtonActionPerformed(ActionEvent event) {
        // System.out.println("Create Account Button Clicked");
        Name = NameJTextField.getText();
        Accountnum = Integer.parseInt(AccountnumJTextField.getText());
        Balance = Integer.parseInt(BalanceJTextField.getText());

        displayJTextArea.setText(Name + " " + Accountnum +" " + Balance);







    }

}

// end  class

Sorry about the really long post just panicing at the moment because I don't know what to fix first to move forward!

Also I'm only doing this with 2 months so I'm not really up on the lingo!

[Steve Luke]

The first thing i'm stuck with is I don't really understand the "Has a " relationship. Like the customer has Accounts but how do I actually link them??

The 'Has-A' relationship is pretty self explanatory (i.e. an object of one type contains, holds, or owns an object of the other type). The way this works in Java is the use of a variable of the appropriate type. For example:

public class Customer
{
    private Account account;

If the Customer can have more than one Account then use a List<Account> (read: a List of Accounts) instead of an Account. How do you get an Account into the Customer? There are basically 3 ways, (1) the Customer can create the Account itself if it has all the information needed to do so:

public class Customer
{
    private Account account = new Account();

    //... or ...
    public Customer(/*...*/ String acntID)
    {
        this.account = new Account(acntID);

(2) the Account can be passed into the Customer class via the constructor. You usually use this way if the Customer must have an Account in order to exist (and usually if it has the same Account for the life of the Customer).

public class Customer
{
    private Account account;

    public Customer(/*...*/ Account acnt)
    {
        this.account = acnt;

Finally (3) you can pass the Account in to the Customer via a 'setter' method.

public class Customer
{
    private Account account;

    public void setAccount(Account acnt)
    {
        this.account = acnt;

In your case, your Account Has-A Customer, and you are saying that the Customer also Has-A Account. So you will need to keep these two in sync. One possible way, since you pass the Customer into the Account as a parameter in its constructor, would be to have the Account pass itself to the Customer as part of its constructor. something like:

public class BankAccount
{
    //...
    Customer customer;

    public BankAccount(Customer customer)
    {
        this.customer = customer;
        this.customer.setAccount(this);
        //...
    }
    //...

[fred rosenberger]

Don't take this the wrong way, but what possible reason do you have for writing almost 700 lines of code when you don't seem to understand what you need to be doing?

Good software design starts with pencil, paper, and your brain. you design at a high level what things should look like and what they should do.

You then write your code in TINY chunks. I never write more than 5 lines before I compile and test.

You want to write code in atomic pieces. What I mean by that is that you can write an account class, and nothing else. you can write code (that you may eventually throw away) to test it and verify it works - that it is rock solid. Once you KNOW your account class works, you can write a person class that has-a account. You then don't need to worry about the account class because you know it is good - you just test the person class until it is rock solid.

Once your person class is tested and rock solid, you can work on your Bank class, and then whatever comes next. Once you have all those working, you then start your GUI code.

If you try and do it all at once, you are doomed to failure.

[Winston Gutkowski]

fred rosenberger wrote:If you try and do it all at once, you are doomed to failure.

@Trish: And further to what Fred said, I would suggest very strongly that you separate your "banking" classes from your GUI entirely (possibly even putting them in a different package).
Bank Accounts (and Customers) existed long before we had computers and terminals to write fancy display systems for; so try and separate the business of banking from that of display. You'll also find that it helps an awful lot when you come to writing test modules.

Steve Luke wrote:If the Customer can have more than one Account then use a List<Account> (read: a List of Accounts) instead of an Account...

<nitpick>
In this particular case I think a Set would be better, since you're not likely to want duplicate Accounts for a Customer (or indeed duplicate Customers for an Account, if that's the way Trish decides to go - I have to admit a slight preference for the latter).
</nitpick>

Winston (old DBA)

[Trish Murphy]

Thanks so much for all the help and advice guys. I'm going to sit down and strip it back now and get everything working step by step, Its my first project and I wasn't sure how to approach it so I dived in foolishly!!! Just one thing you say to separate the gui should I take it out of the main class completely and create a domain class??

[Winston Gutkowski]

Trish Murphy wrote:Thanks so much for all the help and advice guys. I'm going to sit down and strip it back now and get everything working step by step, Its my first project and I wasn't sure how to approach it so I dived in foolishly!!! Just one thing you say to separate the gui should I take it out of the main class completely and create a domain class??

Well, I'm afraid I'm no expert on GUIs, but I'd have thought that one of any size would involve quite a lot of classes.

What I can tell you is that a class called Account should be exactly that: a bank account, NOT its visual representation; so I'd be leery of any Account class that included references to any classes beginning with 'J' (JPanel, JFrame, JComponent... etc) or any System.out calls, unless they're there purely for testing or debugging.

HIH

Winston

[fred rosenberger]

something you might want to read up on is the MVC design principle...Model, View, Controller. The basic idea is that you can separate out these three things - they are completely independent of each other. A device that tells time is the classic example...

The model is how you represent the data inside the computer. A clock may use a pendulum, a radio-isotope decaying, a quartz crystal vibrating, sand falling, or any of several other ways to mark the passage of time. The point is, it doesn't matter how you do it - you pick the one that is best for the technology you have available.

Next is the view. The view asks the model for the time, then displays it to the user. It could post it as "12:17 pm", or be the hands on a clock face, or blinking lights on a binary clock...again, it doesn't matter. the view just asks the model for the data - it doesn't care how the model gets/creates/keeps track of stuff.

Finally, there is the controller. This is how the user interacts with the device. there could be a stem on a watch you pull/push and twist. There could be buttons you press to do different things. Maybe you implement speech recognition. Again, the controller doesn't care how the view displays the data or how the model does its part...

All three do have to talk to each other, but all three can be written independently of each other, and you can - if you design it carefully - replace any one of the three and not impact the other two at all...

I don't think at this point you need to learn any of the MVC frameworks (struts, for example), but the concept is a good thing to start thinking about now.