code: protected void checkMapSize()
    {
      if ((map instanceof EmbeddedSlotMap) && map.size() >= LARGE_HASH_SIZE) {
        SlotMap newMap = new HashSlotMap();
        for (Slot s : map) {
          newMap.addSlot(s);
        }
        map = newMap;
      }
    }
docs: Before inserting a new item in the map, check and see if we need to expand from the embedded
  map to a HashMap that is more robust against large numbers of hash collisions.