Сложна. :С

if (args[0].equals("-c")) {
            createPerson(args[1], args[2], args[3]);
        }

public static void createPerson(String name, String sexType, String BirthDate) throws ParseException {
        Date birthdayDate = simpleDateFormat.parse(BirthDate);
        Person person;
        if (sexType.equals("м")) {
            person = Person.createMale(name, birthdayDate);
            allPeople.add(person);
            System.out.println(allPeople.indexOf(person));
        } else if (sexType.equals("ж")) {
            person = Person.createFemale(name, birthdayDate);
            allPeople.add(person);
            System.out.println(allPeople.indexOf(person));
        }
    }

if (args[0].equals("-i")) {
            person = allPeople.get(Integer.parseInt(args[1]));
            personPrint(person);
        }

public static void personPrint (Person person)   {
        int id = allPeople.indexOf(person);
        String sexType;
        if(allPeople.get(id).getSex().equals(Sex.FEMALE)) {
            sexType = "ж";
        } else {
            sexType = "м";
        }
        System.out.println(person.getName() + " " + sexType + " " + simpleDateFormat2.format(person.getBirthDate()));

    }

if (args[0].equals("-u")) {
            updatePerson(args[1], args[2], args[3], args[4]);
        }

public static void updatePerson(String idChar, String name, String sexType, String BirthDate) throws ParseException {
        int id = Integer.parseInt(idChar);
        Date date = simpleDateFormat.parse(BirthDate);
        allPeople.get(id).setName(name);
        allPeople.get(id).setBirthDate(date);
        if (sexType.equals("м")) {
            allPeople.get(id).setSex(Sex.MALE);
        } else {
            allPeople.get(id).setSex(Sex.FEMALE);
        }

public static void deletePerson(String idChar)  {
        int id = Integer.parseInt(idChar);
        allPeople.get(id).setName(null);
        allPeople.get(id).setBirthDate(null);
        allPeople.get(id).setSex(null);
    }