MatrixMultiply.java

public class MatrixMultiply {

    static void printMatrix(double[][] a) {
        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[0].length; j++) {
                System.out.print(a[i][j] + " ");
            }
            System.out.println();
        }
        System.out.println();
    }

    static double[][] multiply(double[][] a, double[][] b) {

        if (a[0].length != b.length) {
            throw new RuntimeException("Matrix are not compatible");
        }

        double[][] c = new double[a.length][b[0].length];

        for (int i = 0; i < c.length; i++) {
            for (int j = 0; j < c[0].length; j++) {

                for (int k =0 ; k < c[0].length; k++) {
                    c[i][j] = a[i][k] * b[k][j] + c[i][j];
                }

            }
        }

        return c;

    }

}