atmRefactor.java

package com.anton;

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

public class atm {
    public static void main(String[] args) {



        try (Connection connect = DriverManager.getConnection("jdbc:mysql://localhost:3306/atm", "root", "Element1991");
             Statement stmt = connect.createStatement();
             Scanner scan = new Scanner(System.in)) {
            // initialize and connect into our db.
//            Class.forName("com.mysql.jdbc.Driver"); - DO NOT NEED -
//            Connection connect = DriverManager.getConnection("jdbc:mysql://localhost:3306/atm", "root", "Element1991");
            // Statement obj : used for SENDING a static SQL statement and returning the results it produces.
//            Statement stmt = connect.createStatement();
            // createStatement() : creates a Statement object for SENDING SQL statements to the database.

//            Scanner scan = new Scanner(System.in);
            System.out.println("Hi, Welcome To Your ATM.");
            System.out.println();
            System.out.println("Please, Enter Your Pin Number.");
            int pin = scan.nextInt();
            /**
             * ResultSet object : table of data representing a database result set,
             ** which is usually generated by executing a statement that queries the database. When it executes the
             *** query through the Statement object, stmt .
             */
//            String query = "SELECT * FROM new_table where ac_no=" +pin;

            String query = "SELECT * FROM new_table where ac_no=?";
            PreparedStatement pstmt = connect.prepareStatement(query);
            pstmt.setInt(1, pin);
            ResultSet rs = pstmt.executeQuery();

            // Run a check if pin (aka ac_no) matches.
//            ResultSet rs = stmt.executeQuery(query);
            String name = null;
            int balance=0;
            int count=0;
            /**
             * "while there is a change in ResultSet, run while loop..."
             * pin = ` ac_no ` - so when user enters pin the program SELECTS the appropriate row/column.
             ** If successful ( i.e. a change in ResultSet ), the while loop runs.
             */
            while (rs.next()) {
                name = rs.getString(3);
                balance = rs.getInt(4);
                count++;
            }


//            int userChoice;
            int depositAmount = 0;
            int withdrawAmount = 0;

                    // "if while loop is ran more than 0 times, run this code block."
                    if (count>0) {
                        System.out.println("Hi, " +name);
                        System.out.println();
                        while (true) {
                            System.out.println("Press 1 to check balance.");
                            System.out.println("Press 2 to deposit.");
                            System.out.println("Press 3 to withdraw.");
                            System.out.println("Press 4 to print receipt.");
                            System.out.println("Press 5 to exit.");

                            System.out.println();
                            System.out.println("Enter your choice : ");
                            int userChoice = scan.nextInt();
                            transactionType choice = transactionType.values()[userChoice - 1];
                            switch (choice) {
                                case CHECK_BALANCE:
                                    System.out.println("You're balance is : " +balance);
                                    System.out.println();
                                    break;
                                case DEPOSIT:
                                    System.out.println("How much would you like to deposit?");
                                    depositAmount = scan.nextInt();
                                    balance += depositAmount;
                                    // SQL DB //
                                    String depositQuery = "UPDATE new_table SET balance = " +balance+ " WHERE ac_no = " +pin;
                                    int bal = stmt.executeUpdate(depositQuery);
                                    System.out.println("Successfully deposited, your current balance is " +balance);
                                    System.out.println();
                                    break;
                                case WITHDRAW:
                                    System.out.println("How much would you like to withdraw?");
                                    withdrawAmount = scan.nextInt();
                                    if (withdrawAmount > balance) {
                                        System.out.println("Error: insufficient balance.");
                                        System.out.println();
                                    } else {
                                        balance -= withdrawAmount;
                                        // SQL DB //
                                        String withdrawQuery = "UPDATE new_table SET balance = " +balance+ " WHERE ac_no = " +pin;
                                        int subtract = stmt.executeUpdate(withdrawQuery);
                                        System.out.println("Successful withdraw, your current balance is " + balance);
                                        System.out.println();
                                        break;
                                        }
                                case PRINT_RECEIPT:
                                    System.out.println("Thank You.");
                                    System.out.println("Your current balance is : " +balance);
                                    System.out.println("Withdraw amount : " +withdrawAmount);
                                    System.out.println("Deposited amount : " +depositAmount);
                                    System.out.println();
                                    break;
                            }
                            if (choice == transactionType.EXIT) {
                                System.out.println("Thank you, come again!");
                                break;
                            }
                        }
                    } else {
                        System.out.println("Wrong Pin Number Entered.");
                    }

        } catch (Exception e) {
            e.printStackTrace();
        }






    }
}