if (!studentGroup.checkStudentUsernames(studentUsernames)) { throw new InvalidSituationServiceException(); }
    public boolean run(Integer executionCourseID, Integer studentGroupID, Integer groupPropertiesID,            List studentUsernames) throws FenixServiceException, ExcepcaoPersistencia {        final StudentGroup studentGroup = rootDomainObject.readStudentGroupByOID(studentGroupID);        if (studentGroup == null) {            throw new InvalidArgumentsServiceException();        }        final Grouping grouping = studentGroup.getGrouping();        final IGroupEnrolmentStrategyFactory enrolmentGroupPolicyStrategyFactory = GroupEnrolmentStrategyFactory                .getInstance();        final IGroupEnrolmentStrategy strategy = enrolmentGroupPolicyStrategyFactory                .getGroupEnrolmentStrategyInstance(grouping);        if (!strategy.checkStudentsUserNamesInGrouping(studentUsernames, grouping)) {            throw new InvalidArgumentsServiceException();        }        if (!studentGroup.checkStudentUsernames(studentUsernames)) {            throw new InvalidSituationServiceException();        }        for (final String studentUsername : (List<String>) studentUsernames) {            Attends attend = grouping.getStudentAttend(studentUsername);            attend.removeStudentGroups(studentGroup);        }        return true;    }