Question

Convert this code written in Python into Java:

valid = False;

while(valid == False):

   username = input ("Please enter a username:")

   length = len(username);

   if(length < 8 or length > 15):

       print("Username must be between 8 and 15 characters.")

   else:

      

       if(username.isalnum() == False):

           print("Username must contain only alphanumeric characters.");

       else:

           count = 0;

           inx = 0;

           for ch in username:

               if(ch.isdigit() and inx == 0):

                   print("The first character in your username cannot be a digit")

                   count = -1

                   break

               if(ch.isdigit() and inx > 0):

                   count = 1

                   break

               inx = inx+1

           if(count == 1):  

               for ch in username:

                   if(ch.islower()):

                       count = 2

                       break

                  

           if(count == 2):  

               for ch in username:

                   if(ch.isupper()):

                       count = 3

                       break

          

           if(count == 0):      

               print("Your username must contain at least one digit")  

                              

           if(count == 1):      

               print("Your username must contain at least one lowercase character")  

              

           if(count == 2):

               print("Your username must contain at least one uppercase character")

           if(count == 3):

               valid = True  

if(valid == True):

   print("Your username is valid!")

Answer 1

JAVA CODE:

import java.util.Scanner;

public class Main {

    public static void main(String[] args){

        Scanner scan = new Scanner(System.in);

        boolean valid = false;

        int count, inx;

        while(valid == false){

            System.out.print("Please enter a username: ");

            String username = scan.next();

            int length = username.length();

            if(length < 8 || length > 15){

                System.out.println("Username must be between 8 and 15 characters.");

            }

            else{

                if(username.matches("[A-Za-z0-9]+") == false){

                    System.out.println("Username must contain only alphanumeric characters.");

                }

                else{

                    count = 0;

                    inx = 0;

                    for(int i = 0; i < length; i++){

                        if(Character.isDigit(username.charAt(i)) && inx == 0){

                            System.out.println("The first character in your username cannot be a digit");

                            count = -1;

                            break;

                        }

                        if(Character.isLowerCase(username.charAt(i)) && inx > 0){

                            count = 1;

                            break;

                        }

                        inx = inx + 1;

                    }

                    if(count == 1){

                        for(int i = 0; i < length; i++){

                            if(Character.isLowerCase(username.charAt(i))){

                                count = 2;

                                break;

                            }

                        }

                    }

                    if(count == 2){

                        for(int i = 0; i < length; i++){

                            if(Character.isUpperCase(username.charAt(i))){

                                count = 3;

                                break;

                            }

                        }

                    }

                    if(count == 0){

                        System.out.println("Your username must contain at least one digit");

                    }

                    if(count == 1){

                        System.out.println("Your username must contain at least one lowercase character");

                    }

                    if(count == 2){

                        System.out.println("Your username must contain at least one uppercase character");

                    }

                    if(count == 3){

                        valid = true;

                    }

                }

            }

        }

        if(valid){

            System.out.println("Your username is valid!");

        }

        scan.close();

    }

}

SAMPLE OUTPUT:

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