code: private void addNeighborGroup(Collection<String> neighborGroups, Tile tile, int ox, int oy)
      {
          final Tile neighbor = map.getTile(tile.getInTileX() + ox, tile.getInTileY() + oy);
          if (neighbor != null)
          {
              final String neighborGroup = getNeighborGroup(tile, neighbor);
              if (neighborGroup != null)
              {
                  neighborGroups.add(neighborGroup);
              }
          }
      }
docs: Add the neighbor group if exists.
  
  @param neighborGroups The current neighbor groups.
  @param tile The current tile reference.
  @param ox The horizontal offset in tile.
  @param oy The vertical offset in tile.