if (studentGroup.getAttends().contains(attend) || !this.getAttends().contains(attend)) { throw new DomainException(this.getClass().getName(), ""); }
if (studentGroup.getAttends().contains(attend)) throw new DomainException(this.getClass().getName(), "errors.existing.studentEnrolment"); else if(!this.getAttends().contains(attend)) throw new DomainException(this.getClass().getName(), "errors.notExisting.studentInGroupig");
    private void checkForStudentsInStudentGroupsAndGrouping(List<IStudent> students) {        for (IStudent student : students) {            IAttends attend = getStudentAttend(student);            for (final IStudentGroup studentGroup : this.getStudentGroups()) {                if (studentGroup.getAttends().contains(attend) || !this.getAttends().contains(attend)) {                    throw new DomainException(this.getClass().getName(), "");                }            }        }    }