code: public boolean removeUserById(int id) {
  		Iterator<User> it = users.iterator();
  		while (it.hasNext())
  			if (it.next().getId() == id) {
  				it.remove();
  				return true;
  			}
  		return false;
  	}
docs: Removes the user with a given id.
  
  @param id the id
  @return true, if successful