public void addPoint(PolygonPoint p){
  p.setPrevious(_last);
  p.setNext(_last.getNext());
  _last.setNext(p);
  _points.add(p);
}

public void addPoint ( PolygonPoint p ) { p . setPrevious ( _last ) ; p . setNext ( _last . getNext ( ) ) ; _last . setNext ( p ) ; _points . add ( p ) ; }
will add a point after the last point added
