Exception in Thread "Main" java.land.Nullpointerexception com.Login.Login.mai(Login.java:18)

Question

Today I tried to make a login system (again), only this time I used a array one-dimensional to guard my values. When I ran my program, Eclipse had an error (null pointer to be more specific), my theory is that assign a value to array caused the error.

Follow my code below:

package com.Login;
import java.util.Scanner;
import java.util.Random;

public class Login {
    Random r = new Random();

    String[] valores;
    boolean isSessionValid;
    int sessID = r.nextInt();

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


        System.out.println("Digite o nome do usuário:");
        log.valores[1] = in.nextLine();
        System.out.println("Digite sua senha:");
        log.valores[2] = in.nextLine();

        System.out.println("Digite novamente a senha:");
        log.valores[3] = in.nextLine();
        if(log.valores[3].equals(log.valores[1])){
            System.out.println("Você está logado!");
            log.isSessionValid = true;
            System.out.println("Sua Sessão é:"+log.sessID);
        }
    }

}

Simply the code assigns the user name to log.valores[1] and the password to log.valores[2] and log.valores[3] serves only to confirm the password.

Answer 1

This error indicates that you are trying to access an object that has not been initialized. It will solve by initializing the vector. Apparently 4 positions are sufficient. Maybe up to 3 if you start with index 0:

String[] valores = new String[4];

I put in the Github for future reference.

The code has other bad things, but I’ll stick to the question.

See more in What is Nullpointerexception and what are its main causes?.