BankingSystem.java

package sqlconnect;

import java.sql.*;
import java.util.Scanner;

public class BankingSystem {
    private static final String URL = "jdbc:mysql://localhost:3306/bankdb";
    private static final String USER = "root"; //  username
    private static final String PASS = "1331"; //  password

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        try (Connection conn = DriverManager.getConnection(URL, USER, PASS)) {
            int choice;
            do {
                System.out.println("\n--- ATM / Banking System ---");
                System.out.println("1. Create Account");
                System.out.println("2. Login");
                System.out.println("3. Exit");
                System.out.print("Enter choice: ");
                choice = sc.nextInt();

                switch (choice) {
                    case 1 -> createAccount(conn, sc);
                    case 2 -> login(conn, sc);
                    case 3 -> System.out.println("Thank you for using our ATM.");
                    default -> System.out.println("Invalid choice!");
                }
            } while (choice != 3);

        } catch (SQLException e) {
            e.printStackTrace();
        }
        sc.close();
    }

    // Create a new account
    private static void createAccount(Connection conn, Scanner sc) throws SQLException {
        sc.nextLine(); // clear buffer
        System.out.print("Enter Name: ");
        String name = sc.nextLine();
        System.out.print("Set a 4-digit PIN: ");
        int pin = sc.nextInt();

        String sql = "INSERT INTO accounts (name, pin, balance) VALUES (?, ?, 0)";
        try (PreparedStatement ps = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) {
            ps.setString(1, name);
            ps.setInt(2, pin);
            ps.executeUpdate();

            try (ResultSet rs = ps.getGeneratedKeys()) {
                if (rs.next()) {
                    System.out.println("Account created successfully! Your Account No is: " + rs.getInt(1));
                }
            }
        }
    }

    // Login
    private static void login(Connection conn, Scanner sc) throws SQLException {
        System.out.print("Enter Account No: ");
        int accNo = sc.nextInt();
        System.out.print("Enter PIN: ");
        int pin = sc.nextInt();

        String sql = "SELECT * FROM accounts WHERE account_no = ? AND pin = ?";
        try (PreparedStatement ps = conn.prepareStatement(sql)) {
            ps.setInt(1, accNo);
            ps.setInt(2, pin);
            try (ResultSet rs = ps.executeQuery()) {
                if (rs.next()) {
                    System.out.println("Welcome, " + rs.getString("name"));
                    accountMenu(conn, sc, accNo);
                } else {
                    System.out.println("Invalid Account No or PIN.");
                }
            }
        }
    }

    // Account menu after login
    private static void accountMenu(Connection conn, Scanner sc, int accNo) throws SQLException {
        int choice;
        do {
            System.out.println("\n--- Account Menu ---");
            System.out.println("1. Check Balance");
            System.out.println("2. Deposit");
            System.out.println("3. Withdraw");
            System.out.println("4. View Transactions");
            System.out.println("5. Logout");
            System.out.print("Enter choice: ");
            choice = sc.nextInt();

            switch (choice) {
                case 1 -> checkBalance(conn, accNo);
                case 2 -> deposit(conn, sc, accNo);
                case 3 -> withdraw(conn, sc, accNo);
                case 4 -> viewTransactions(conn, accNo);
                case 5 -> System.out.println("Logging out...");
                default -> System.out.println("Invalid choice!");
            }
        } while (choice != 5);
    }

    private static void checkBalance(Connection conn, int accNo) throws SQLException {
        String sql = "SELECT balance FROM accounts WHERE account_no = ?";
        try (PreparedStatement ps = conn.prepareStatement(sql)) {
            ps.setInt(1, accNo);
            try (ResultSet rs = ps.executeQuery()) {
                if (rs.next()) {
                    System.out.println("Current Balance: ₹" + rs.getDouble("balance"));
                }
            }
        }
    }

    private static void deposit(Connection conn, Scanner sc, int accNo) throws SQLException {
        System.out.print("Enter deposit amount: ");
        double amount = sc.nextDouble();

        String sql = "UPDATE accounts SET balance = balance + ? WHERE account_no = ?";
        try (PreparedStatement ps = conn.prepareStatement(sql)) {
            ps.setDouble(1, amount);
            ps.setInt(2, accNo);
            ps.executeUpdate();
        }

        recordTransaction(conn, accNo, "Deposit", amount);
        System.out.println("₹" + amount + " deposited successfully.");
    }

    private static void withdraw(Connection conn, Scanner sc, int accNo) throws SQLException {
        System.out.print("Enter withdrawal amount: ");
        double amount = sc.nextDouble();

        String checkSql = "SELECT balance FROM accounts WHERE account_no = ?";
        try (PreparedStatement psCheck = conn.prepareStatement(checkSql)) {
            psCheck.setInt(1, accNo);
            try (ResultSet rs = psCheck.executeQuery()) {
                if (rs.next()) {
                    double currentBalance = rs.getDouble("balance");
                    if (currentBalance >= amount) {
                        String updateSql = "UPDATE accounts SET balance = balance - ? WHERE account_no = ?";
                        try (PreparedStatement psUpdate = conn.prepareStatement(updateSql)) {
                            psUpdate.setDouble(1, amount);
                            psUpdate.setInt(2, accNo);
                            psUpdate.executeUpdate();
                        }
                        recordTransaction(conn, accNo, "Withdraw", amount);
                        System.out.println("₹" + amount + " withdrawn successfully.");
                    } else {
                        System.out.println("Insufficient funds.");
                    }
                }
            }
        }
    }

    private static void viewTransactions(Connection conn, int accNo) throws SQLException {
        String sql = "SELECT type, amount, date FROM transactions WHERE account_no = ? ORDER BY date DESC";
        try (PreparedStatement ps = conn.prepareStatement(sql)) {
            ps.setInt(1, accNo);
            try (ResultSet rs = ps.executeQuery()) {
                System.out.println("---- Transaction History ----");
                while (rs.next()) {
                    System.out.println(rs.getString("date") + " | " + rs.getString("type") + " | ₹" + rs.getDouble("amount"));
                }
            }
        }
    }

    private static void recordTransaction(Connection conn, int accNo, String type, double amount) throws SQLException {
        String sql = "INSERT INTO transactions (account_no, type, amount) VALUES (?, ?, ?)";
        try (PreparedStatement ps = conn.prepareStatement(sql)) {
            ps.setInt(1, accNo);
            ps.setString(2, type);
            ps.setDouble(3, amount);
            ps.executeUpdate();
        }
    }
}