code: public double pathLength(double delta, Point2D.Double... controlPoints)
      {
          if (controlPoints.length != length)
          {
              throw new IllegalArgumentException("control-points length not "+length);
          }
          double[] cp = convert(controlPoints);
          return pathLength(delta, cp);
      }
docs: Calculates path length
  @param delta
  @param controlPoints
  @return