code: public DistanceElement getElement(long id) {
  		
  		if (!vector.containsKey(id))
  			vector.put(id, new DistanceElement(id));
  		
  		return vector.get(id);
  	}
docs: Gets an element of the distance vector, based on the given node id. If a DistanceElement object with the given id does
  not exist in the vector, a new object with the id is added to it. Then, the element with the given id as key is returned
  in the end.
  
  @param id the id whose associated DistanceElement object is to be returned
  @return the value to which the specified id is mapped