Question

3. Use a text editor to create a comma-delimited file of user IDs and passwords. Revise any one of the games you have created throughout this book so the user must first enter a correct ID and its associated password before playing. Save the program as GameWithPassword.java.

Answer 1

Note: Done accordingly. Please comment for any problem. Please Uprate. Thanks

Please add code to open your previous game when login is successful. I already highlighted that part,

Code:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class GameWithPassword {

   static int checkLoginDetails(String username, String password) {
       int status = 0; //status 0 means username does not exist
       try {
           //opening file
           BufferedReader br = new BufferedReader(new FileReader("loginDatabase.txt"));
           String line = null;
           //reading line by line
           while ((line = br.readLine()) != null) {
               String[] values = line.split(",");//split username and password
               if (values[0].equals(username)) {//checking for username
                   if (values[1].equals(password)) {//checking for password
                       br.close();
                       return 1;//both are correct
                   } else {
                       status = 2; //username is correct but password is wrong
                   }
               }
           }
           br.close();
       } catch (IOException e) {
           System.out.println("File does not exist.");
           e.printStackTrace();
       }
       return status;
   }

   public static void main(String[] args) {
       //creating instance of scanner class
       Scanner read = new Scanner(System.in);
       String username,password;
       int result;
       //reading username
       System.out.print("Please give username :");
       username=read.nextLine();
       //reading password
       System.out.print("Please give password :");
       password=read.nextLine();
       //Checking login details
       result=checkLoginDetails(username,password);
       //printing appropriate message
       if(result==0){
           System.out.println("Username does not exist.");
       }else if(result==2){
           System.out.println("Password is not correct for username : "+username);
       }else{//login is successful
           System.out.println("Success");
           //ADD CODE TO OPEN GAME
       }
       read.close();
   }

}

Outputs: