docs: public final synchronized long nextId(Object obj)
  	{
  		if (tc.isEntryEnabled()) Tr.entry(tc, "nextId", obj);
  		
  		long id = _idCount++;
  
  		// Keep incrementing the id until we
  		// find one that hasn't been reserved.
  		while (_idMap.get(id) != null)
  		{
  			id = _idCount++;
  		}
  
  		// Add the new id to the map associating
  		// it with the given object.
  		_idMap.put(id, obj);
  
  		if (tc.isEntryEnabled()) Tr.exit(tc, "nextId", new Long(id));
  
  		return id;
  	}