public void selectionSort() {

        for(int i = 0; i < persons.size();i++) {
            int smallest = i;
            for(int j = i+1;j < persons.size(); j++) {
                int compare = persons.get(smallest).compareTo(persons.get(j));
                if (compare > 0){
                    smallest = j;
                }
            }
            Person tempPerson = persons.get(i);
            persons.set(i, persons.get(smallest));
            persons.set(smallest, tempPerson);
        }

    }