public boolean isRectangle(){
		if(points.size() != 4) return false;
		ShapePoint p1 = (ShapePoint) points.get(0);
		ShapePoint p2 = (ShapePoint) points.get(1);
		ShapePoint p3 = (ShapePoint) points.get(2);
		ShapePoint p4 = (ShapePoint) points.get(3);
		if(p1.isInLineWith(p2) 
			&& p2.isInLineWith(p3)
			&& p3.isInLineWith(p4)
			&& p4.isInLineWith(p1)) return true;
		return false;
	}