for (final IStudentGroup studentGroup : shift.getAssociatedStudentGroups()) { if (studentGroup.getGrouping().equals(this)) {
for (final IStudentGroup studentGroup : this.getStudentGroups()) { if (studentGroup.getGrouping().equals(shift)) {
    public List<IStudentGroup> readAllStudentGroupsBy(IShift shift) {        final List<IStudentGroup> result = new ArrayList<IStudentGroup>();        for (final IStudentGroup studentGroup : shift.getAssociatedStudentGroups()) {            if (studentGroup.getGrouping().equals(this)) {                result.add(studentGroup);            }        }        return result;    }