code: private SyncState checkForElementStates(SyncState... states) {
  		if (this.elements != null) {
  			for (T elem : this.elements) {
  				for (SyncState state : states) {
  					if (elem.getSyncState() != state)
  						return elem.getSyncState();
  				}
  			}
  		}
  		return null;
  	}
docs: check all elements, if their state is one of the given states
  @param states to check against
  @return null, if all elements have a state out of the requested states,
  else return the first element state that differs