code: public static double getClockwiseAngleBetweenThreePoints(final Point2D p0, final Point2D c, final Point2D p1)
      {
          final Point2D a = c.sub(p1);
  
          final Point2D b = c.sub(p0);
  
          return Math.atan2(a.getY(), a.getX()) - Math.atan2(b.getY(), b.getX());
      }
docs: Returns the clockwise angle between three points.
  It starts at p0, that goes clock-wise around c until it reaches p1
  
  @param p0
  @param c
  @param p1
  @return