for (Registration registration : RootDomainObject.getInstance().getStudents()) {
for (Registration registration : RootDomainObject.getInstance().getRegistrations()) {
	public static Registration readStudentByNumberAndDegreeType(Integer number, DegreeType degreeType) {		for (Registration registration : RootDomainObject.getInstance().getStudents()) {			if (registration.getNumber().equals(number) && registration.getDegreeType().equals(degreeType)) {				return registration;			}		}		return null;	}