Question

I am creating a program that will allow users to sign in with a username and password. Their information is saved in a text file. The information in the text file is saved as such:

Username

Password

I have created a method that will take the text file and convert into an array list. Once the username and password is found, it will be removed from the arraylist and will give the user an opportunity to sign in with a different username and password. Also, the user has 3 tries to correctly sign in, if they are unable the program will terminate.

The problem with my program is that my program will not compile and I am getting issues such as: error: illegal start of type and error: <identifier> expected. These errors are coming from my method that converts the text file into an arraylist. Also, there maybe more bugs in there that I am unware of. Any help would be appreciated. Below is my code:

import java.io.*;
import java.util.*;
public class LoginPagev2
{
   public static void main(String[] args) throws IOException
   {
       String answ;
       String user;
       String pass ;
       int counter = 0;
       Scanner keyboard = new Scanner(System.in);
       System.out.println("Welcome! This program will allow you to sign in with a username and password you created.");
       System.out.println("If you fail to login correctly 3 times, this program will terminate. You can only sign in once per username.");
       System.out.println("If you wish to sign in into the same account twice, you must restart the program.");
       while(true)
       {   System.out.print("Would you like to sign in? (Y/N): ");
           answ = keyboard.nextLine();
           if(answ.equalsIgnoreCase("N"))
           {
               System.out.print("Goodbye!");
               System.exit(0);
           }
           System.out.print("What is your username?: " );
           user = keyboard.nextLine();
           System.out.print("What is your password?: ");
           pass = keyboard.nextLine();
           for (int i = 0; i<list().size(); i++)
           while((!list().contains(user) || !list().contains(pass)) || counter < 3)
           {
               ++ counter;
               if(list().contains(user) || list().contains(pass))
               {
                       list().remove(user, pass);
                       System.out.print("Congrats! You successfully signed in!");
                       counter = 0;
                       break;
               }
               if(counter==3)
               {
                   System.out.println("You have attempted you max amount of tries. This program will now end.");
                   System.exit(0);
               }
               else
               {
                   System.out.println("This is not valid. Please try again");
                   System.out.print("What is your username?: " );
                   user = keyboard.nextLine();
                   System.out.print("What is your password?: ");
                   pass = keyboard.nextLine();
                   //for (int i = 0; i<list().size(); i++)
               }
           }
           System.out.print("Would you like to sign in with another account? (Y/N): ");
           String rep = keyboard.nextLine;
           if(rep.equalsIgnoreCase("N"))
           {
               System.out.print("Goodbye!");
               System.exit(0);
           }
           else
               continue;
       }
      
   }          
  
   public static ArrayList<String> list()
   {
       BufferedReader reader = new BufferedReader(new FileReader("loginInfo.txt"));
       String line;
       ArrayList<String> arr = new ArrayList<String> ();
       while ((line = reader.readLine()) != null)
       {
           arr.add(line);
       }
       reader.close();
   }
   return arr;
}
  

Answer 1

You are getting an illegal start of type error because, in list() method, you are not returning the arr inside the method. The code to return the array list arr is outside the method. It should be inside the method.

public static ArrayList<String> list() { try { BufferedReader reader = new BufferedReader (new FileReader("loginInfo.txt")); String line; ArrayList<String> arr = new ArrayList<String>(); while ((line = reader.readLine()) != null) { arr.add(line); reader.close(); return arr; } catch (Exception ex) { return null;

Also, there should be the try-catch block to handle any exception that might occur on file processing. And it should return in case of any exception.

I found other errors in your code, which are as follows:

• When you are checking for username and password in the ArrayList, the logical operator between the two conditions should be AND(&&) not OR(||).
• You cannot remove both username and password from the list in a single call. You need to call it two times to remove username and password.

for (int i = 0; i < list().size(); i++) { while ((!list().contains (user) || !list().contains (pass)) || counter <3) { ++counter; if (list().contains (user) && list().contains (pass)) { //list().remove (user, pass); list().remove (user); list().remove (pass); System.out.print("Congrats! You successfully signed in!"); counter = 0; break;

• You forgot to put brackets in the nextLine() method:

System.out.print("Would you like to sign in with another account? (Y/N): "); String rep = keyboard.nextLine(); if (rep.equalsIgnoreCase ("N")) { System.out.print("Goodbye!"); System.exit(0); } else { continue;

Below is the sample output after fixing your code:

este si me pas com run: Welcome! This program will allow you to sign in with a username and password you created. If you fail to login correctly 3 times, this program will terminate. You can only sign in once per username. If you wish to sign in into the same account twice, you must restart the program. Would you like to sign in? (Y/N): Y What is your username?: myuser What is your password?: myPwd This is not valid. Please try again What is your username?: myuser What is your password?: myPassword Congrats! You successfully signed in! Congrats! You successfully signed in! Would you like to sign in with another account? (Y/N): Goodbye! BUILD SUCCESSFUL (total time: 20 seconds)

Below is the content of the input file:

myuser
myPassword

This completes the requirement. Let me know if you have any questions.

Thanks!