if (entry._key instanceof LongValue) { long key = entry._key.toLong(); if (key >= _nextAvailableIndex) _nextAvailableIndex = key+1; }
_nextAvailableIndex = 0;  for (Entry entry = _head; entry != null; entry = entry._next) { updateNextAvailableIndex(entry); }
  private void updateNextAvailableIndex(Entry entry)  {    if (entry._key instanceof LongValue)      {	long key = entry._key.toLong();	if (key >= _nextAvailableIndex)	  _nextAvailableIndex = key+1;      }  }