code: protected boolean checkTileIndex (int tileIndex)
      {
          int tcount = getTileCount();
          if (tileIndex >= 0 && tileIndex < tcount) {
              return true;
          } else {
              log.warning("Requested invalid tile [tset=" + this + ", index=" + tileIndex + "].",
                          new Exception());
              return false;
          }
      }
docs: Used to ensure that the specified tile index is valid.