"String index out of range: 5"

Question

There is an error mentioned in the question in my java program.

The program is a barcode reader. The user informs the digits of the code (except the last one). The sum of the numbers q are in odd position, and those in odd position. Then there are other calculations (which I will do later) that result in the last digit (the one that was not informed by the user).

I reduced it to 12 to 4 digits informed by the user, to make it easier to follow the code. It is running, but when arriving on line 26 gives error (first is, but I believe in the second too):

import java.util.Scanner;

public class Main {
    public static void main (String[] args) {

        Scanner sc = new Scanner(System.in);
        String codigo;

        do {
            System.out.println("\n\nInforme os primeiros 4 caracteres do codigo de barras: \n");
            codigo = sc.nextLine();

            if (codigo.length() != 4) {
                System.out.println("\n\nO numero informado nao corresponde a 4 caracteres.");
            }

        } while (codigo.length() != 4); 

        int somaImpar = 0;

        for (int i = 0; i <= codigo.length(); i = i + 2) {
            int numConvertido = Integer.parseInt(codigo.substring(i, (i + 1)));
            System.out.println("i: " + i);
            somaImpar = somaImpar + numConvertido;

            if (i == 2) {
                System.out.println("Soma dos impares: " + somaImpar);
            }
        }

        int somaPar = 0;

        for (int i = 1; i <= codigo.length(); i = i + 2) {
            int numConvertido2 = Integer.parseInt(codigo.substring(i, (i + 1)));
            System.out.println("i: " + i);
            somaPar = somaPar + numConvertido2;

            if (i == 3) {
                System.out.println("Soma dos pares: " + somaPar);
            }
        }
    } 
}

I’ve tried to change the condition of the i < 5 for i == 4, put other values, but still giving error.

Answer 1

The problem is yes in yours for (and it would happen in both).

for (int i = 0; i < 5; i = i + 2)

You say he should iterate while the i is less than 5; has the user type 4 numbers. Right away it’s a problem, because if you went through the digits one by one you would have a total of 5 (positions 0, 1, 2, 3 and 4 of the variable codigo).

But your mistake breaks in this line:

int numConvertido = Integer.parseInt(codigo.substring(i, (i + 1)));

Your counter increments two by iteration of for (i = i + 2), then think of the third execution, when i = 4; the numConvertido will receive codigo.substring(4, 5), when actually the code only has 4 digits.

You need to review this for the two points:

• the stopping condition should be i < codigo.length()
• iteration should be only one (i++)