code: public static List<String> replaceNullValueWithEmptyGroup(@Nonnull final List<String> groups) {
  		Check.notNull(groups, "groups");
  
  		final List<String> result = new ArrayList<String>(groups.size());
  		for (final String group : groups) {
  			if (group == null) {
  				result.add(EMPTY_GROUP);
  			} else {
  				result.add(group);
  			}
  		}
  		for (int i = result.size(); i < MIN_GROUP_SIZE; i++) {
  			result.add(EMPTY_GROUP);
  		}
  		return result;
  	}
docs: Replaces all {@code null} values in the given list of groups with {@code VersionNumber#EMPTY_GROUP}.
  
  @param groups
  list of numbers of a version number
  @return a new list of groups without {@code null} values