Comparator

comparator.java

List<Person> persons = personsExtracter.getPersons();
Collections.sort(persons, new AgeComparator());

public class AgeComparator implements Comparator<Person> {
    @Override
    public int compare(Person o1, Person o2) {
        Integer age1 = o1.getAge();
        Integer age2 = o2.getAge();
        return age1.compareTo(age2);
    }
}