JTreeのノード選択で生成された直角多角形の角を丸める

public static List<Point2D> flatteningStepsOnRightSide(
    List<Point2D> list, double arc) {
  int sz = list.size();
  for (int i = 0; i < sz; i++) {
    int i1 = (i + 1) % sz;
    int i2 = (i + 2) % sz;
    int i3 = (i + 3) % sz;
    Point2D pt0 = list.get(i);
    Point2D pt1 = list.get(i1);
    Point2D pt2 = list.get(i2);
    Point2D pt3 = list.get(i3);
    double dx1 = pt2.getX() - pt1.getX();
    if (Math.abs(dx1) > 1.0e-1 && Math.abs(dx1) < arc) {
      double max = Math.max(pt0.getX(), pt2.getX());
      replace(list, i, max, pt0.getY());
      replace(list, i1, max, pt1.getY());
      replace(list, i2, max, pt2.getY());
      replace(list, i3, max, pt3.getY());
    }
  }
  return list;
}

private static void replace(List<Point2D> list, int i, double x, double y) {
  list.remove(i);
  list.add(i, new Point2D.Double(x, y));
}