Help PHC ROBOT

import java.util.InputMismatchException;
import java.util.Scanner;

public class InflationRateCalculator {
    // Arrays to store usernames and passwords of users
    static String[] usernames = new String[10];
    static String[] passwords = new String[10];
    // Counter to keep track of number of users
    static int userCount = 0;
    // boolean to check if user has logged in
    static boolean loggedIn = false;
    // String to store the product name
    static String product = "";
    // String to store the current user
    static String currentUser = "";
    
    public static void main(String[] args) {
        // Create a new scanner object to read input from user
        Scanner scanner = new Scanner(System.in);
        // Variables to store previous and current year
        int previousYear = 0;
        int currentYear = 0;
        
        while (true) {
            if (!loggedIn) {
                // User is not logged in, display login menu
                System.out.println("Welcome Inflation Rate for Goods and Services Calculator\n");
                System.out.println("Please choose an option:\n");
                System.out.println("1. Log in");
                System.out.println("2. Create account");
                System.out.println("3. Exit\n\n");
                int choice = scanner.nextInt();
                
                switch (choice) {
                    case 1:
                        // User has chosen to log in, prompt for username and password
                        System.out.println("\nEnter username:");
                        String username = scanner.next();
                        System.out.println("\nEnter password:");
                        String password = scanner.next();
                        // Check if username and password are correct
                        if (login(username, password)) {
                            System.out.println("\nLogin successful.");
                            loggedIn = true;
                            currentUser = username;
                        } else {
                            System.out.println("Invalid username or password. Please try again.\n");
                        }
                        break;
                    case 2:
                        // User has chosen to create an account, prompt for username and password
                        System.out.println("\nEnter username:");
                        String newUsername = scanner.next();
                        System.out.println("\nEnter password:");
                        String newPassword = scanner.next();
                        // Check if username already exists
                        if (createAccount(newUsername, newPassword)) {
                            System.out.println("\n\nAccount created successfully.\n");
                        } else {
                            System.out.println("\nUsername already exists. Please choose a different username.\n");
                        }
                        break;
                    case 3:
                        // User has chosen to exit, close scanner and exit program
                        System.out.println("\n\nExiting program...\n");
                        scanner.close();
                        System.exit(0);
                    default:
                        // User has entered an invalid choice
                        System.out.println("\nInvalid choice. Please try again.\n");
                        break;
                }
            } else {
                // User is logged in, display main menu
                System.out.println("\nWelcome, " + currentUser + "!");
                System.out.println("\nPlease choose an option:");
                System.out.println("\n1. Calculate inflation rate");
                System.out.println("\n2. Logout");
                int choice = scanner.nextInt();
                
                switch (choice) {
                    case 1:
                        // User has chosen to calculate inflation rate
                        boolean validInput = false;
                        while (!validInput) {
                            try {
                                // Prompt user for product name, previous year, current year, current price and previous price
                                System.out.println("\nEnter product name :");
                                product = scanner.next();
                                                                
                                System.out.println("\nEnter previous year:");
                                previousYear = scanner.nextInt();
                                System.out.println("\nEnter current year:");
                                currentYear = scanner.nextInt();
                                System.out.println("\nEnter current price:");
                                double cpi = scanner.nextDouble();
                                System.out.println("\nEnter previous price:");
                                double previousCpi = scanner.nextDouble();
                                // Calculate inflation rate and display result
                                double inflationRate = (int) Math.round(cpi - previousCpi) / previousCpi * 100;
                                System.out.println("\nInflation rate for " + previousYear + "-" + currentYear + " (" + product + ") = " + inflationRate + "%");
                                validInput = true;
                            } catch (InputMismatchException e) {
                                // User has entered a non-integer for year or price
                                System.out.println("\nYou entered a non-integer. Please enter integers only.");
                                scanner.next();
                            }
                        }
                        break;
                    case 2:
                        // User has chosen to log out, set loggedIn to false and currentUser to empty string
                        System.out.println("\n\nLogging out...\n\n");
                        loggedIn = false;
                        currentUser = "";
                        break;
                    default:
                        // User has entered an invalid choice
                        System.out.println("\nInvalid choice. Please try again.");
                        break;   
                }
            }
        }
    }
    
    public static boolean login(String username, String password) {
        // Loop through the usernames and passwords arrays to find a match
        for (int i = 0; i < userCount; i++) {
            if (usernames[i].equals(username) && passwords[i].equals(password)) {
                return true;
            }
        }
        // If no match is found, return false
        return false;
    }
    
    public static boolean createAccount(String username, String password) {
        // Loop through the usernames array to check if username already exists
        for (int i = 0; i < userCount; i++) {
            if (usernames[i].equals(username)) {
                return false;
            }
        }
        // If username doesn't exist, add it to the array
        usernames[userCount] = username;
        passwords[userCount] = password;
        userCount++;
        return true;
    }
}