_nextAvailableIndex = 0;
  private void shiftEntries(int index)  {    int capacity = _entries.length;    // we'll be re-addEntry()ing all entries, so it's safe to reset this    _nextAvailableIndex = 0;    for (; index < capacity; index++) {      Entry entry = _entries[index];      if (entry == null)	return;      _entries[index] = null;      addEntry(entry);    }  }