java

/*
Main use of this class:
1. to show welcome message
2. to verify id and pass for already existing user
3. to create new id and pass for new user

Extra use:
1. to create directory and file for user login
*/

package com.company;

import java.io.File;
import java.util.Formatter;
import java.util.Scanner;

public class Welcome {
    // to take user input
    Scanner sc = new Scanner(System.in);

    // constructor
    Welcome() {
        createDir();
        welcomeMessage();
    }

    // used to clear screen
    public static void cls() {
        try {
            new ProcessBuilder("cmd", "/c", "cls").inheritIO().start().waitFor();
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    // to show welcome message
    void welcomeMessage() {
        // showing welcome message
        System.out.println("Welcome to Fahad's Super Shop");
        System.out.println("1. Login");
        System.out.println("2. Registration");
        System.out.print("Please Enter your choice: ");

        String lr = sc.next();
        System.out.println();

        // matching user input and doing action
        if (lr.equals("1")) {
            loginForm();
        } else if (lr.equals("2")) {
            regForm();
        } else {
            System.out.println("Invalid input. try again.\n");
            welcomeMessage();
        }
    }

    // creating directory and login file
    void createDir() {
        File dir = new File("E:/Login");
        dir.mkdir();

        try {
            File login = new File("E:/Login/login.txt");
            login.createNewFile();
        } catch (Exception e) {
            System.out.println("File creation error!");
        }
    }

    // checking for valid login information
    void loginForm() {
        boolean found = false; // to check if the id and pass match
        String id, pass;

        // taking user id and pass.
        System.out.print("Please enter your id: ");
        id = sc.next();
        System.out.print("Please enter your pass: ");
        pass = sc.next();

        try {
            // opening file and reading previously saved information
            File read = new File("E:/Login/login.txt");

            sc = new Scanner(read);
            while (sc.hasNext()) {
                String sTemp = sc.next();
                String[] sTemp1 = sTemp.split(">");

                if (id.equals(sTemp1[0]) && pass.equals(sTemp1[1])) {
                    System.out.println("Login Successful\n");
                    found = true;
                    break;
                }
            }
            //sc.close();
        } catch (Exception e) {
            System.out.println("Please enter valid information!\n");
        }

        // if the id and pass do not match
        if (!found) {
            System.out.println("Please enter valid information!\n");
            loginForm(); // recalling loginForm to enter valid information again (this doesn't work. don't know why)
        }
    }

    // doing registration for new user
    void regForm() {
        String id, pass;

        // taking new id and pass
        System.out.print("Please enter your new id: ");
        id = sc.next();
        System.out.print("Please enter your new pass: ");
        pass = sc.next();

        // writing on file for further use of that id and pass
        try {
            Formatter write = new Formatter("E:/Login/login.txt");
            write.format("%s\n", id + ">" + pass);

            System.out.println("Registration Successful.\n");
            write.close();
        } catch (Exception e) {
            System.out.println("Something went wrong. Registration failed!\n");
            //regForm(); // this doesn't work
        }
    }
}