docs: @SuppressWarnings("WeakerAccess")
      public int floor(double centroid) {
          int floor = IntAVLTree.NIL;
          for (int node = tree.root(); node != IntAVLTree.NIL; ) {
              final int cmp = Double.compare(centroid, mean(node));
              if (cmp <= 0) {
                  node = tree.left(node);
              } else {
                  floor = node;
                  node = tree.right(node);
              }
          }
          return floor;
      }