Java: Login System Won't Work

Question

I've been making a login system prototype for my game, sad thing is it doesn't work! I'm not sure why but here's my code:

This is the code for my main class:`

package darkbyte.tests;

import java.util.Scanner;

public class Main {

    private static FileCreator creator = new FileCreator();
    private static FileReader reader = new FileReader();

    private static void login() {
        Scanner input = new Scanner(System.in);

        boolean passwordExists;

        System.out.println();
        System.out.println("Please enter your username: ");
        String username = input.nextLine();
        System.out.println("Please enter your password: ");
        String password = input.nextLine();

        reader.openFile(username + ".user");
        if(reader.doesStringExist(password)) {
            passwordExists = true;
        } else {
            passwordExists = false;
        }

        reader.closeFile();

        if(passwordExists) {
            System.out.println("Welcome back to Darkbyte " + username + "!");
        } else {
            System.out.println("The password you entered is incorrect!");
            login();
        }
    }

    private static void register() {
        Scanner input = new Scanner(System.in);

        System.out.println();
        System.out.println("Please enter the username you desire: ");
        String username = input.nextLine();
        System.out.println("Please enter the password you desire: ");
        String password = input.nextLine();

        creator.openFile(username + ".user");
        creator.writeString(username);
        creator.writeString(password);
        creator.closeFile();
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.println("Welcome to Darkbyte!");
        System.out.println("Would you like to login or register an account?"); 
        System.out.println("Enter 0 to login and any other number to register: ");
        int choice = input.nextInt();

        if(choice == 0) {
            login();
        } else {
            register();
        }
    }
}

This is the code for my FileCreator class:

package darkbyte.tests;

import java.io.*;

import java.util.*;

public class FileCreator {

    private Formatter format;

    public void openFile(String file) {
        try {
            format = new Formatter(file);
        } catch(Exception e) {
            System.err.println("Darkbyte: There was an error in opening the file!");
        }
    }

    public void closeFile() {
       format.close();
    }

    public void writeInteger(int i) {
        format.format("%i%n", i);
    }

    public void writeFloat(float f) {
        format.format("%f%n", f);
    }

    public void writeString(String s) {
        format.format("%s%n", s);
    }

    public void appendInt(String file, int i) {
        try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(file, true)))) {
            out.println(i);
        }catch (IOException e) {
            System.err.println("Darkbyte: Couldn't find file!");
        }
    }

    public void appendFloat(String file, float f) {
        try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(file, true)))) {
            out.println(f);
        }catch (IOException e) {
            System.err.println("Darkbyte: Couldn't find file!");
        }
    }

    public void appendString(String file, String s) {
        try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(file, true)))) {
            out.println(s);
       }catch (IOException e) {
             System.err.println("Darkbyte: Couldn't find file!");
        }
    }
}

This is the code for my FileReader class:

package darkbyte.tests;

import java.io.*;

import java.util.*;

public class FileReader {

    private Scanner scanner;

    public void openFile(String file) {
        try {
            scanner = new Scanner(new File(file));
        } catch(Exception e) {
            System.err.println("Darkbyte: Couldn't find file!");
        }
    }

    public void closeFile() {
        scanner.close();
    }

    public void readInt(int i, int lookingFor) {
        while(i != lookingFor) {
            if(scanner.hasNext()) {
                i = Integer.parseInt(scanner.next());
            }
        }
    }

    public void readFloat(float f, float lookingFor) {
        while(f != lookingFor) {
            if(scanner.hasNext()) {
                f = Float.parseFloat(scanner.next());
            }
        }
    }

    public void readString(String s, String lookingFor) {
        while(s != lookingFor) {
            if(scanner.hasNext()) {
                s = scanner.next();
            }
        }
    }

    public boolean doesIntExist(int i) {
        boolean intIsFound = false;
        int tempInt;

        while(scanner.hasNext()) {
            if(!intIsFound) {
                tempInt = Integer.parseInt(scanner.next());
                if(tempInt == i) {
                    intIsFound = true;
                } else {
                    intIsFound = false;
                }
            }
        }

        return intIsFound;
    }

    public boolean doesFloatExist(float f) {
        boolean floatIsFound = false;
        float tempFloat;

        while(scanner.hasNext()) {
            if(!floatIsFound) {
                tempFloat = Float.parseFloat(scanner.next());
                if(tempFloat == f) {
                    floatIsFound = true;
                } else {
                    floatIsFound = false;
                }
            }
        }

        return floatIsFound;
    }

    public boolean doesStringExist(String s) {
        boolean stringIsFound = false;
        String tempString;

        while(scanner.hasNext()) {
            if(!stringIsFound) {
                tempString = scanner.next();
                if(tempString == s) {
                    stringIsFound = true;
                } else {
                    stringIsFound = false;
                }
            }
        }

        return stringIsFound;
    }
}

The issue is, when I try to login, even if my username and password are correct, it still says that my details are incorrect!

I'm not sure why but can you help me out please!

if(tempString == s) . This is not how you compare strings in java. — OldProgrammer, Jun 30 '15 at 12:02

score 1 · Accepted Answer · answered Jun 30 '15 at 12:04

I think the error is in

if(tempString == s) {
    stringIsFound = true;
} else {
    stringIsFound = false;
}

Change it to:

if(tempString.equals(s)) {
    stringIsFound = true;
} else {
    stringIsFound = false;
}

Always use equals when comparing Strings, otherwise you are comparing their reference and not their value.

score 0 · Answer 2 · answered Jun 30 '15 at 12:03

0

You cannot compare strings like this:

if(tempString == s) {

You must use equals... So instead of == compare with equals() and fill your boolean like this:

stringIsFound = tempString.equals(s);

answered Jun 30 '15 at 12:03

Jordi Castilla

26,609
8
70
109

Actually, you can compare Strings like that. The only problem is, you might think you are comparing values, while you are comparing references. – Stultuske Jun 30 '15 at 12:05
1

then you don't compare strings, you compare `objects`, or in this case `String` objects... dont confuse the OP.... – Jordi Castilla Jun 30 '15 at 12:06
You mean to say Strings are not objects? You are comparing the Strings, just not their values. – Stultuske Jun 30 '15 at 12:08
I mean string is a word that means text... `String` is a java object... I repeat... don't confuse OP please – Jordi Castilla Jun 30 '15 at 12:08
have you noted the `UPPERCASE` firts letter in `String` word... right??? – Jordi Castilla Jun 30 '15 at 12:09

score -1 · Answer 3 · answered Jun 30 '15 at 12:04

Your code is quite unlogical. comparing a password you entered by command line to another one you enter through the command line?

As OldProgrammer already stated: you'll need to use the .equals method to compare the Strings on value equality. == will only test them for referential equality.

Also, a small remark. Code like this:

if(reader.doesStringExist(password)) {
            passwordExists = true;
        } else {
            passwordExists = false;
        }

can easily be refactored to a slightly more efficiënt and easier to read snippet:

passwordExists = reader.doesStringExist(password);

I didn't think about the fact that it was a boolean, thanks for that! — Ammar Tarajia, Jun 30 '15 at 12:08

Java: Login System Won't Work

3 Answers3