Matrix multiplication using arrays

Question

I was trying to write a program on matrix multiplication which should return an identity matrix. But, it is not working. I am using a multi-dimensional array. Can anyone help me with this?

Answer 1

You can try with the below code, which will help you get an identity matrix:

public class Intellipaat {

    Double[][] A = { { 4.00, 3.00 }, { 2.00, 1.00 } };

    Double[][] B = { { -0.500, 1.500 }, { 1.000, -2.0000 } };

    public static Double[][] multiple(Double[][] A, Double[][] B) {

        int aRows = A.length;

        int aColumns = A[0].length;

        int bRows = B.length;

        int bColumns = B[0].length;

        if (aColumns != bRows) {

            throw new IllegalArgumentException("A:Rows: " + aColumns + " did not match B:Columns " + bRows + ".");

        }

        Double[][] C = new Double[aRows][bColumns];

        for (int i = 0; i < aRows; i++) {

            for (int j = 0; j < bColumns; j++) {

                C[i][j] = 0.00000;

            }

        }

        for (int i = 0; i < aRows; i++) { // aRow

            for (int j = 0; j < bColumns; j++) { // bColumn

                for (int k = 0; k < aColumns; k++) { // aColumn

                    C[i][j] += A[i][k] * B[k][j];

                }

            }

        }

        return C;

    }

    public static void main(String[] args) {

        Intellipaat matrix = new Intellipaat();

        Double[][] result = multiple(matrix.A, matrix.B);

        for (int i = 0; i < 2; i++) {

            for (int j = 0; j < 2; j++)

                System.out.print(result[i][j] + " ");

            System.out.println();

        }

    }

}

I hope this will help.

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