code: public static double lengthSquared(double x, double y, double z) {
          return x * x + y * y + z * z;
      }
docs: Get the length squared of a 3-dimensional double-precision vector.
  
  @param x The vector's x component
  @param y The vector's y component
  @param z The vector's z component
  
  @return the length squared of the given vector
  
  @author F. Neurath