code: private static double[] crossProduct(double[] u, double[] v) {
          return new double[]{(u[1] * v[2]) - (v[1] * u[2]), (u[2] * v[0]) - (v[2] * u[0]), (u[0] * v[1]) - (v[0] * u[1])};
      }
docs: Cross product of two 3D coordinates
  
  @param u either 3D coordinates
  @param v other 3D coordinates
  @return the cross-product