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How to code a very simple login system with java


Question

I need to create a system that checks a file for the username and password and if it is correct, it says whether or not in a label. So far I have been able to simply make one username and password equal to the variable, but need to link it to a file somehow. I am a noob programmer so lots of help is appreciated. Here is what I have under my authenticate button.

String pass;
String user;
user = txtUser.getText();
pass = txtPass.getText();

if(pass.equals("blue") && user.equals("bob") ){
    lblDisplay.setText("Credentials Accepted.");
}
else{
    lblDisplay.setText("Please try again.");
}     
2013/05/18
1
6
5/18/2013 7:22:26 PM

Accepted Answer

You will need to use java.util.Scanner for this issue.

Here is a good login program for the console:

import java.util.Scanner; // I use scanner because it's command line.

public class Login {
public void run() {
    Scanner scan = new Scanner (new File("the\\dir\\myFile.extension"));
    Scanner keyboard = new Scanner (System.in);
    String user = scan.nextLine();
    String pass = scan.nextLine(); // looks at selected file in scan

    String inpUser = keyboard.nextLine();
    String inpPass = keyboard.nextLine(); // gets input from user

    if (inpUser.equals(user) && inpPass.equals(pass)) {
        System.out.print("your login message");
    } else {
        System.out.print("your error message");
    }
}
} 

Of course, you will use Scanner scanner = new Scanner (File toScan); but not for user input.

Happy coding!

As a last note, you are at least a decent programmer if you can make Swing components.

2013/05/18
11
5/18/2013 7:34:31 PM

Check this code :

import java.util.Scanner;

public class Main {

public static void main(String[] args) throws IllegalAccessException {

    String username ;
    String password;
    String yes_0r_no;
    String scann;
    String passscan;

    Scanner scan = new Scanner(System.in);
    Scanner scanner = new Scanner(System.in);

    Scanner name = new Scanner(System.in);
    System.out.println("Username:");
    username = name.next().toLowerCase();

    Scanner pass = new Scanner(System.in);
    System.out.println("Password:");
    password = pass.next().toLowerCase();


    System.out.println("You are logged in");

    Scanner ask = new Scanner(System.in);
    System.out.println("Do you want to check this or not(yes or no) :");

     yes_0r_no = ask.next().toLowerCase();



    while (true){
        if (yes_0r_no.equals("yes")){
            System.out.println("Username:");
          scann = scan.next().toLowerCase();
          if (scann == username) {
              continue;
          }
        System.out.println("Password");
        passscan = scanner.next().toLowerCase();
        if (passscan.equals(password)) {
            System.out.println("You are logged in");
            break;

        }if (!password.equals(passscan)) {
            throw new IllegalAccessException();
            }
        }

        if (yes_0r_no.equals("no"))
            break ;



    }


}

}

2020/01/03

this is my first code on this site try this

import java.util.Scanner;
public class BATM {

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

    String username;
    String password;

    System.out.println("Log in:");
    System.out.println("username: ");
    username = input.next();

    System.out.println("password: ");
    password = input.next();

    //users check = new users(username, password);

    if(username.equals(username) && password.equals(password)) 
        System.out.println("You are logged in");



}

}
2015/10/02

Code

import java.util.Scanner;

public class LoginMain {

public static void main(String[] args) {

    String Username;
    String Password;

    Password = "123";
    Username = "wisdom";

    Scanner input1 = new Scanner(System.in);
    System.out.println("Enter Username : ");
    String username = input1.next();

    Scanner input2 = new Scanner(System.in);
    System.out.println("Enter Password : ");
    String password = input2.next();

    if (username.equals(Username) && password.equals(Password)) {

        System.out.println("Access Granted! Welcome!");
    }

    else if (username.equals(Username)) {
        System.out.println("Invalid Password!");
    } else if (password.equals(Password)) {
        System.out.println("Invalid Username!");
    } else {
        System.out.println("Invalid Username & Password!");
    }

}

}
2016/11/29

import java.util.Scanner;

public class LoginMain {

public static void main(String[] args) {

    String Username;
    String Password;

    Password = "123";
    Username = "wisdom";

    Scanner input1 = new Scanner(System.in);
    System.out.println("Enter Username : ");
    String username = input1.next();

    Scanner input2 = new Scanner(System.in);
    System.out.println("Enter Password : ");
    String password = input2.next();

    if (username.equals(Username) && password.equals(Password)) {

        System.out.println("Access Granted! Welcome!");
    }

    else if (username.equals(Username)) {
        System.out.println("Invalid Password!");
    } else if (password.equals(Password)) {
        System.out.println("Invalid Username!");
    } else {
        System.out.println("Invalid Username & Password!");
    }
2020/04/22

Map<String, String> d = new HashMap<>();

void input(String u, String p, String e) {
    read();
    if (e.equals("login")) login(u, p);
    else if (e.equals("register")) register(u, p);
    write();
}

void read() {
    d = new HashMap<>();
    String s = "";
    try {
        s = new String(Files.readAllBytes(Paths.get("data.txt")));
    }catch(IOException e) {
        e.printStackTrace();
    }
    String [] pairs = s.split("\n");
    for (int i = 0; i < pairs.length; i++) {
        d.put(pairs[i].split(",")[0], pairs[i].split(",")[1]);
    }
}

void write() {
    try (FileWriter m = new FileWriter("data.txt")) {
        for (Map.Entry<String, String> entry : d.entrySet()) {
            m.write(entry.getKey() + "," + entry.getValue() + "\n");    
        }
        m.close();
    }catch (IOException e) {
        e.printStackTrace();
    }
}

boolean login(String u, String p) {
    return (d.get(u).equals(p)) ? true : false;
}

boolean register(String u, String p) {
    if (d.containsKey(u)) return false;
    d.put(u, p);
    return true;
}
2020/07/15