How to scan the matrix using only one for?

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The circumstances are in the code that works:

    String[][] compras = new String[][] { { "item 1", "1.70" }, { "item 2", "39.90" }, { "item 3", "9.90" }, { "item 4", "4.90" }, { "item 5", "7.90" } };
            
    int soma = 0;
    for (int i = 0; i < compras.length; i++) {
        for (int j = 0; j < compras[i].length; j++) {

            if (j == 1) {
                soma = (int) (soma + Double.parseDouble(compras[i][j]));
            }
        }
    }

    System.out.println("Total das compras: R$ " + soma);
}
java array matrix optimizing

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1 answer

2

In fact, the internal tie makes no sense, it travels through a dimension but only wants one element, so use that element instead of going through all of them. In practice you only need index 1 and not go through it all. So is the way j is variant, but the if makes it only useful as constant.

class Main {
    public static void main (String[] args) {
        String[][] compras = new String[][] {
                { "item 1", "1.70" }, { "item 2", "39.90" }, { "item 3", "9.90" }, { "item 4", "4.90" },
                { "item 5", "7.90" } };
        int soma = 0;
        for (int i = 0; i < compras.length; i++) soma = (int)(soma + Double.parseDouble(compras[i][1]));
        System.out.println("Total das compras: R$ " + soma);
    }
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

Another important detail is that it seems to be using monetary values that cannot be represented with the type Double.

  • Thank you so much!! helped me a lot!! success!

  • @Mariana see on [tour] that you can accept the answer if she solved your problem.

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