else professorShip.setResponsibleFor(false);
professorShip.setResponsibleFor(responsibleFor);
    public static IProfessorship create(Boolean responsibleFor, IExecutionCourse executionCourse, ITeacher teacher, Double hours) throws MaxResponsibleForExceed, InvalidCategory{               if(responsibleFor == null || executionCourse == null || teacher == null)            throw new NullPointerException();                IProfessorship professorShip = new Professorship();                       if(hours == null)            professorShip.setHours(new Double(0.0));        else            professorShip.setHours(hours);        if (responsibleFor.booleanValue()) {                        ResponsibleForValidator.getInstance().validateResponsibleForList(teacher, executionCourse, professorShip);            professorShip.setResponsibleFor(true);        }        else            professorShip.setResponsibleFor(false);                professorShip.setExecutionCourse(executionCourse);        professorShip.setTeacher(teacher);                return professorShip;    }