_nextAvailableIndex = 0;
  public void clear()  {    if (_isDirty) {      _entries = new Entry[_entries.length];      _isDirty = false;    }        _size = 0;    _head = _tail = _current = null;        for (int j = _entries.length - 1; j >= 0; j--) {      _entries[j] = null;    }  }