BankingSystem.java

import java.awt.*; // import karta abstract window toolkit package for creating gui elements
import java.awt.event.ActionEvent; // actionevent class for handling button click
import java.util.ArrayList; // arraylist and list for creating and managing list of trans.
import java.util.HashMap; //hashmap and map for storing and retrieving acc. by account number
import java.util.List; 
import java.util.Map;
import javax.swing.*; //import the swing gui framework components

// defines class bankingsystem that recieve from jframe (window in gui a-pplication)
public class BankingSystem extends JFrame {
    // accounts - hashmap to store account object with the account no. as his key
    // transaction - arraylist to store all transaction object
    // tabbedpane - it is going to hold diifernt tabs of the application
    private final Map<String, Account> accounts = new HashMap<>();
    private final List<Transaction> transactions = new ArrayList<>();
    private final JTabbedPane tabbedPane;
    
    //Create Account Tab
    // create account tab to collect name, account number, and initial balance // button to sumit the account creation form
    private JTextField createNameField;
    private JTextField createAccountNumberField;
    private JTextField createInitialBalanceField;
    private JButton createAccountButton;
    
    //Deposit Tab
    // collect ccount number and deposit amount and button to sumit deposit transaction
    private JTextField depositAccountNumberField;
    private JTextField depositAmountField;
    private JButton depositButton;
    
    // Withdraw Tab
    // collect account number and withdrawal amount and button to sumit the withdrawal transaction
    private JTextField withdrawAccountNumberField;
    private JTextField withdrawAmountField;
    private JButton withdrawButton;
    
    // Transaction History 
    private JTextArea transactionHistoryArea;
    private JTextField historyAccountNumberField;
    private JButton showHistoryButton;
    
    // Constructor for  BankingSystem class
    // window title to Banking System
    // window size (600x500px)
    // the default close operation to exit the application when the window is closed
    // Centers the window on the screen (setLocationRelativeTo(null)
    public BankingSystem() {
        setTitle("Banking System");
        setSize(600, 500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        
        tabbedPane = new JTabbedPane();
        
        // Creating Tabs
        // Creates new JTabbedPane for tabbed interface
        // ya add bhi kar dega 4 tabs with their respective panels
        // add tabbed pane to the main window
        tabbedPane.addTab("Create Account", createCreateAccountPanel());
        tabbedPane.addTab("Deposit", createDepositPanel());
        tabbedPane.addTab("Withdraw", createWithdrawPanel());
        tabbedPane.addTab("Transaction History", createTransactionHistoryPanel());
        
        add(tabbedPane);
    }
    
    // ui panel creation method
    //  new panel banayega with GridBagLayout for flexible component positioning
    // banayega GridBagConstraints for controlling the layout
    // ya set kar dega 5px padding around components
    // ya set components to anchor to the west (left) side
    private JPanel createCreateAccountPanel() {
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.anchor = GridBagConstraints.WEST;
        
        // Naming the fields
        // set grid postion(o,o) for the label
        // add kar label for customer name
        // move grid pos. (1,0) for text field
        // create kar text field for createName input width of 20 columns
        // add text field to the panel  
        gbc.gridx = 0;
        gbc.gridy = 0;
        panel.add(new JLabel("Customer Name:"), gbc);
        
        gbc.gridx = 1;
        createNameField = new JTextField(20);
        panel.add(createNameField, gbc);
        
        // acc no. field

        gbc.gridx = 0;
        gbc.gridy = 1;
        panel.add(new JLabel("Account Number:"), gbc);
        
        gbc.gridx = 1;
        createAccountNumberField = new JTextField(20);
        panel.add(createAccountNumberField, gbc);
        
        // initial balance field
        gbc.gridx = 0;
        gbc.gridy = 2;
        panel.add(new JLabel("Initial Balance:"), gbc);
        
        gbc.gridx = 1;
        createInitialBalanceField = new JTextField(20);
        panel.add(createInitialBalanceField, gbc);
        
        // create balance field
        gbc.gridx = 0;
        gbc.gridy = 3;
        gbc.gridwidth = 2;
        gbc.anchor = GridBagConstraints.CENTER;
        createAccountButton = new JButton("Create Account");
        createAccountButton.addActionListener((ActionEvent e) -> {
            createAccount();
        });
        panel.add(createAccountButton, gbc);
        
        return panel;
    }
    
    private JPanel createDepositPanel() {
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.anchor = GridBagConstraints.WEST;
        
        // Account Number field
        gbc.gridx = 0;
        gbc.gridy = 0;
        panel.add(new JLabel("Account Number:"), gbc);
        
        gbc.gridx = 1;
        depositAccountNumberField = new JTextField(20);
        panel.add(depositAccountNumberField, gbc);
        
        // Amount field
        gbc.gridx = 0;
        gbc.gridy = 1;
        panel.add(new JLabel("Amount:"), gbc);
        
        gbc.gridx = 1;
        depositAmountField = new JTextField(20);
        panel.add(depositAmountField, gbc);
        
        // Deposit button
        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.gridwidth = 2;
        gbc.anchor = GridBagConstraints.CENTER;
        depositButton = new JButton("Deposit");
        depositButton.addActionListener((ActionEvent e) -> {
            deposit();
        });
        panel.add(depositButton, gbc);
        
        return panel;
    }
    
    private JPanel createWithdrawPanel() {
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.anchor = GridBagConstraints.WEST;
        
        // Account Number field
        gbc.gridx = 0;
        gbc.gridy = 0;
        panel.add(new JLabel("Account Number:"), gbc);
        
        gbc.gridx = 1;
        withdrawAccountNumberField = new JTextField(20);
        panel.add(withdrawAccountNumberField, gbc);
        
        // Amount field
        gbc.gridx = 0;
        gbc.gridy = 1;
        panel.add(new JLabel("Amount:"), gbc);
        
        gbc.gridx = 1;
        withdrawAmountField = new JTextField(20);
        panel.add(withdrawAmountField, gbc);
        
        // Withdraw button
        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.gridwidth = 2;
        gbc.anchor = GridBagConstraints.CENTER;
        withdrawButton = new JButton("Withdraw");
        withdrawButton.addActionListener((ActionEvent e) -> {
            withdraw();
        });
        panel.add(withdrawButton, gbc);
        
        return panel;
    }
    
    private JPanel createTransactionHistoryPanel() {
        JPanel panel = new JPanel(new BorderLayout(5, 5));
        
        // Top panel for account number input
        JPanel topPanel = new JPanel(new FlowLayout(FlowLayout.LEFT, 5, 5));
        topPanel.add(new JLabel("Account Number:"));
        
        historyAccountNumberField = new JTextField(15);
        topPanel.add(historyAccountNumberField);
        
        showHistoryButton = new JButton("Show History");
        showHistoryButton.addActionListener((ActionEvent e) -> {
            showTransactionHistory();
        });
        topPanel.add(showHistoryButton);
        
        panel.add(topPanel, BorderLayout.NORTH);
        
        // Transaction history area
        transactionHistoryArea = new JTextArea();
        transactionHistoryArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(transactionHistoryArea);
        
        panel.add(scrollPane, BorderLayout.CENTER);
        
        return panel;
    }
    
    private void createAccount() {
        String name = createNameField.getText().trim();
        String accountNumber = createAccountNumberField.getText().trim();
        String initialBalanceStr = createInitialBalanceField.getText().trim();
        
        if (name.isEmpty() || accountNumber.isEmpty() || initialBalanceStr.isEmpty()) {
            JOptionPane.showMessageDialog(this, "Please fill in all fields", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        try {
            double initialBalance = Double.parseDouble(initialBalanceStr);
            if (initialBalance < 0) {
                JOptionPane.showMessageDialog(this, "Initial balance cannot be negative", "Error", JOptionPane.ERROR_MESSAGE);
                return;
            }
            
            if (accounts.containsKey(accountNumber)) {
                JOptionPane.showMessageDialog(this, "Account number already exists", "Error", JOptionPane.ERROR_MESSAGE);
                return;
            }
            
            Account account = new Account(name, accountNumber, initialBalance);
            accounts.put(accountNumber, account);
            
            // Record the transaction
            Transaction transaction = new Transaction(accountNumber, "Account Creation", initialBalance, initialBalance);
            transactions.add(transaction);
            
            JOptionPane.showMessageDialog(this, """
                                                Account created successfully!
                                                Name: """ + name + "\n" +
                "Account Number: " + accountNumber + "\n" +
                "Initial Balance: " + initialBalance, "Success", JOptionPane.INFORMATION_MESSAGE);
            
            // Clear fields
            createNameField.setText("");
            createAccountNumberField.setText("");
            createInitialBalanceField.setText("");
            
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(this, "Please enter a valid number for initial balance", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }
    
    private void deposit() {
        String accountNumber = depositAccountNumberField.getText().trim();
        String amountStr = depositAmountField.getText().trim();
        
        if (accountNumber.isEmpty() || amountStr.isEmpty()) {
            JOptionPane.showMessageDialog(this, "Please fill in all fields", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        if (!accounts.containsKey(accountNumber)) {
            JOptionPane.showMessageDialog(this, "Account not found", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        try {
            double amount = Double.parseDouble(amountStr);
            if (amount <= 0) {
                JOptionPane.showMessageDialog(this, "Amount must be positive", "Error", JOptionPane.ERROR_MESSAGE);
                return;
            }
            
            Account account = accounts.get(accountNumber);
            double newBalance = account.getBalance() + amount;
            account.setBalance(newBalance);
            
            // Record the transaction
            Transaction transaction = new Transaction(accountNumber, "Deposit", amount, newBalance);
            transactions.add(transaction);
            
            JOptionPane.showMessageDialog(this, 
                """
                Deposit successful!
                Account: """ + accountNumber + "\n" +
                "Amount deposited: " + amount + "\n" +
                "New balance: " + newBalance, "Success", JOptionPane.INFORMATION_MESSAGE);
            
            // Clear fields
            depositAccountNumberField.setText("");
            depositAmountField.setText("");
            
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(this, "Please enter a valid number for amount", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }
    
    /**
     * 
     */
    private void withdraw() {
        String accountNumber = withdrawAccountNumberField.getText().trim();
        String amountStr = withdrawAmountField.getText().trim();
        
        if (accountNumber.isEmpty() || amountStr.isEmpty()) {
            JOptionPane.showMessageDialog(this, "Please fill in all fields", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        if (!accounts.containsKey(accountNumber)) {
            JOptionPane.showMessageDialog(this, "Account not found", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        try {
            double amount = Double.parseDouble(amountStr);
            if (amount <= 0) {
                JOptionPane.showMessageDialog(this, "Amount must be positive", "Error", JOptionPane.ERROR_MESSAGE);
                return;
            }
            
            Account account = accounts.get(accountNumber);
            if (account.getBalance() < amount) {
                JOptionPane.showMessageDialog(this, "Insufficient funds", "Error", JOptionPane.ERROR_MESSAGE);
                return;
            }
            
            double newBalance = account.getBalance() - amount;
            account.setBalance(newBalance);
            
            // Record the transaction
            Transaction transaction = new Transaction(accountNumber, "Withdrawal", -amount, newBalance);
            transactions.add(transaction);
            
            JOptionPane.showMessageDialog(this, 
                """
                Withdrawal successful!
                Account: """ + accountNumber + "\n" +
                "Amount withdrawn: " + amount + "\n" +
                "New balance: " + newBalance, "Success", JOptionPane.INFORMATION_MESSAGE);
            
            // Clear fields
            withdrawAccountNumberField.setText("");
            withdrawAmountField.setText("");
            
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(this, "Please enter a valid number for amount", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }
    
    private void showTransactionHistory() {
        String accountNumber = historyAccountNumberField.getText().trim();
        
        if (accountNumber.isEmpty()) {
            JOptionPane.showMessageDialog(this, "Please enter an account number", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        if (!accounts.containsKey(accountNumber)) {
            JOptionPane.showMessageDialog(this, "Account not found", "Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        
        Account account = accounts.get(accountNumber);
        transactionHistoryArea.setText("");
        
        // Add account info
        transactionHistoryArea.append("Account Holder: " + account.getName() + "\n");
        transactionHistoryArea.append("Account Number: " + account.getAccountNumber() + "\n");
        transactionHistoryArea.append("Current Balance: " + account.getBalance() + "\n\n");
        transactionHistoryArea.append("Transaction History:\n");
        
        // Add transactions
        boolean found = false;
        for (Transaction transaction : transactions) {
            if (transaction.getAccountNumber().equals(accountNumber)) {
                found = true;
                transactionHistoryArea.append(String.format(
                    "Type: %-15s Amount: %10.2f Balance: %10.2f\n",
                    transaction.getType(),
                    transaction.getAmount(),
                    transaction.getBalanceAfter()
                ));
            }
        }
        
        if (!found) {
            transactionHistoryArea.append("No transactions found for this account.\n");
        }
    }
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            new BankingSystem().setVisible(true);
        });
    }
    
    // Account class to store account information
    private class Account {
        private final String name;
        private final String accountNumber;
        private double balance;
        
        public Account(String name, String accountNumber, double balance) {
            this.name = name;
            this.accountNumber = accountNumber;
            this.balance = balance;
        }
        
        public String getName() {
            return name;
        }
        
        public String getAccountNumber() {
            return accountNumber;
        }
        
        public double getBalance() {
            return balance;
        }
        
        public void setBalance(double balance) {
            this.balance = balance;
        }
    }
    
    // Transaction class to store transaction information
    private class Transaction {
        private final String accountNumber;
        private final String type;
        private final double amount;
        private final double balanceAfter;
        private final String timestamp;
        
        public Transaction(String accountNumber, String type, double amount, double balanceAfter) {
            this.accountNumber = accountNumber;
            this.type = type;
            this.amount = amount;
            this.balanceAfter = balanceAfter;
            this.timestamp = java.time.LocalDateTime.now().toString();
        }
        
        public String getAccountNumber() {
            return accountNumber;
        }
        
        public String getType() {
            return type;
        }
        
        public double getAmount() {
            return amount;
        }
        
        public double getBalanceAfter() {
            return balanceAfter;
        }
        
        public String getTimestamp() {
            return timestamp;
        }
    }
}