Validation of log-in by vector (array) .java

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Validation of log-in by vector (array) .java

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#1 by (5 votes)
#2 by (4 votes)

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I'm studying object-oriented vectors and I've decided to do some programming to get things done.

It consists of registering n vectors that will be bank accounts with name, password, account and balance . Using only the console as an interaction, they should be registered in positions in the vector separately each% w / w%.

Next, you should ask for a " log-in" which consists of name and password and both must pass a basic and rustic validation process, which would first be to see if the name typed in the log-in part corresponds to an account registered in the vector and if the answer is true option to enter the password , and the validation of this will be to see if the vector with the name chosen has the password also registered to that the user typed in log-in .

package application;

import java.util.Locale;
import java.util.Scanner;

import entities.ContaBancaria;

public class ProgramContaBancaria {

    public static void main(String[] args) {

        Locale.setDefault(Locale.US);
        Scanner sc = new Scanner(System.in);

        System.out.print("Digite quantas contas serão cadastradas: ");
        int quantidade = sc.nextInt();
        ContaBancaria[] conta = new ContaBancaria[quantidade];

        System.out.println();

        for(int i = 0; i < conta.length; i++) {
        int x = 1;
        x += i; 
        System.out.println("Conta #"+ x);
        System.out.print("Digite o nome da conta para cadastro: ");
        String name = sc.next();
        System.out.print("Digite a senha para cadastro: ");
        int password = sc.nextInt();
        System.out.print("Digite o número da conta para cadastro: ");
        int account = sc.nextInt();
        conta[i] = new ContaBancaria(name, password, account);
        System.out.println();
        }

        System.out.println("Clientes cadastrados com sucesso!");
        System.out.println();
        System.out.println("  Login");
        System.out.print("Name: ");
        String name = sc.next();
        boolean check = false;

        for(int i = 0; i < conta.length; i++) {
            if(conta[i].getName().equals(name) ) {
                    check = true;
            }
            else 
                    check = false;
            }

            if (check = true) {
            System.out.print("Password: ");
            }
            else if (check = false){
                System.out.print("Nome inválido: ");
                String name2 = sc.next();
                name += name2;
        }
        int password = sc.nextInt();

    }

}

So the problem is, the compiler is not "respecting" the new conta(name,password,account,balance) condition.

Regardless of what I do or type it gives as if(check = false){sysout("Nome inválido");}(...) and already executes true .

What's wrong? What could I do to improve / change?

java

asked by anonymous 26.12.2018 / 13:56

2 answers

4

Maybe I'm wrong, but I think comparisons should be made with == and not just = :

if(check == false)

== = > Comparison

= = > Assign value

26.12.2018 / 14:18

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score 5 · Accepted Answer

The error has nothing to do with "the compiler is not respecting the condition". In fact the program is doing exactly what you asked for.

In this case, the if(check = true) snippet is doing the following:

assigning the value true to the variable check
testing this value

It's like you do it in 2 steps:

check = true;
if (check) {
    ....

Yes, note that when the variable is a boolean , I do not have to compare it with true or false . if tests a Boolean value, and since the check variable itself is boolean , I can check it directly. And since the value is true , it will always go into this if .

Of course I could check if its value is equal to true , making if (check == true) , but for Boolean variables this is redundant and unnecessary. However, for comparing values we use the == operator, not = .

That is, if (check = true) causes it to always enter this if - and therefore never reaches if (check = false) . In fact, this if is also wrong. If you want to test if a boolean is false, just do if (! check) ("if check is false").

But since Boolean can only have 2 values (true or false), you do not need to test the same variable again on else . Just do it like this:

if (check) {
    // check é verdadeiro (true)
} else {
    // check é falso (false)
}