How to add two multidimensional array in java?

Question

public class MatrixAddition {

    public static void main(String[] args) {

        int ar1[][] = { { 0, 1, 2 }, { 3, 4, 5 }, { 6, 7, 8 } };
        int ar2[][] = { { 8, 7, 6 }, { 5, 4, 3 }, { 2, 1, 0 } };

        addArray(ar1, ar2);

    }

    private static void addArray(int[][] tmp1, int[][] tmp2) {
        int[][] sum = {};
        System.out.println(" ");
        System.out.println("The sum of the two matrices is");
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                sum[i][j] = tmp1[i][j] + tmp2[i][j];
                System.out.print(sum[i][j] + "  ");
            }

        }

    }

}

output:

The sum of the two matrices is
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0

What do you think int[][] sum = {}; does?

Alexis C.
– Alexis C.

2014-12-28 19:22:40 +00:00
Commented Dec 28, 2014 at 19:22 — Alexis C.
– Alexis C., Commented Dec 28, 2014 at 19:22

Eran · Accepted Answer · 2014-12-28 19:24:07Z

6

Your only problem is that you don't initialize the sum array properly :

int[][] sum = new int[tmp1.length][tmp1[0].length];

You initialize it to an empty array.

answered Dec 28, 2014 at 19:24

Eran

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Comments

Elliott Frisch · Accepted Answer · 2014-12-28 19:25:06Z

0

I don't think you need a sum array, and if you did you would have to size it based on the input arrays.

private static void addArray(int[][] tmp1, int[][] tmp2) {
    System.out.println(" ");
    System.out.println("The sum of the two matrices is");
    for (int i = 0; i < tmp1.length; i++) {
        for (int j = 0; j < tmp1[i].length; j++) {
            if (j != 0) {
                System.out.print(", ");
            }
            int sum = tmp1[i][j] + tmp2[i][j];
            System.out.print(sum);
        }
        System.out.println();
    }
}

answered Dec 28, 2014 at 19:25

Elliott Frisch

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