public static double[][] multiply0(double[][] m1, double[][] m2) {
        double[][] result = new double[4][4];
        result[0][0] = (m2[0][0] * m1[0][0]) + (m2[0][1] * m1[1][0])
                + (m2[0][2] * m1[2][0]) + (m2[0][3] * m1[3][0]);
        result[0][1] = (m2[0][0] * m1[0][1]) + (m2[0][1] * m1[1][1])
                + (m2[0][2] * m1[2][1]) + (m2[0][3] * m1[3][1]);
        result[0][2] = (m2[0][0] * m1[0][2]) + (m2[0][1] * m1[1][2])
                + (m2[0][2] * m1[2][2]) + (m2[0][3] * m1[3][2]);
        result[0][3] = (m2[0][0] * m1[0][3]) + (m2[0][1] * m1[1][3])
                + (m2[0][2] * m1[2][3]) + (m2[0][3] * m1[3][3]);
        result[1][0] = (m2[1][0] * m1[0][0]) + (m2[1][1] * m1[1][0])
                + (m2[1][2] * m1[2][0]) + (m2[1][3] * m1[3][0]);
        result[1][1] = (m2[1][0] * m1[0][1]) + (m2[1][1] * m1[1][1])
                + (m2[1][2] * m1[2][1]) + (m2[1][3] * m1[3][1]);
        result[1][2] = (m2[1][0] * m1[0][2]) + (m2[1][1] * m1[1][2])
                + (m2[1][2] * m1[2][2]) + (m2[1][3] * m1[3][2]);
        result[1][3] = (m2[1][0] * m1[0][3]) + (m2[1][1] * m1[1][3])
                + (m2[1][2] * m1[2][3]) + (m2[1][3] * m1[3][3]);
        result[2][0] = (m2[2][0] * m1[0][0]) + (m2[2][1] * m1[1][0])
                + (m2[2][2] * m1[2][0]) + (m2[2][3] * m1[3][0]);
        result[2][1] = (m2[2][0] * m1[0][1]) + (m2[2][1] * m1[1][1])
                + (m2[2][2] * m1[2][1]) + (m2[2][3] * m1[3][1]);
        result[2][2] = (m2[2][0] * m1[0][2]) + (m2[2][1] * m1[1][2])
                + (m2[2][2] * m1[2][2]) + (m2[2][3] * m1[3][2]);
        result[2][3] = (m2[2][0] * m1[0][3]) + (m2[2][1] * m1[1][3])
                + (m2[2][2] * m1[2][3]) + (m2[2][3] * m1[3][3]);
        result[3][0] = (m2[3][0] * m1[0][0]) + (m2[3][1] * m1[1][0])
                + (m2[3][2] * m1[2][0]) + (m2[3][3] * m1[3][0]);
        result[3][1] = (m2[3][0] * m1[0][1]) + (m2[3][1] * m1[1][1])
                + (m2[3][2] * m1[2][1]) + (m2[3][3] * m1[3][1]);
        result[3][2] = (m2[3][0] * m1[0][2]) + (m2[3][1] * m1[1][2])
                + (m2[3][2] * m1[2][2]) + (m2[3][3] * m1[3][2]);
        result[3][3] = (m2[3][0] * m1[0][3]) + (m2[3][1] * m1[1][3])
                + (m2[3][2] * m1[2][3]) + (m2[3][3] * m1[3][3]);
        return result;
    }