public class Person  implements Comparable<Person>{

    private String id;
    private String name;
    private int credits;

    public Person(String i, String n, int c){
        id = i;
        name = n;
        credits = c;
    }

    public String personInfo(){
        return String.format("%-5s %12s %5d",id,name,credits);
    }

    public int compareTo(Person that) {
        return id.compareTo(that.id);
    }

    public static void main(String[]args){
        System.out.println(new Person("A01","juan garcia",7).personInfo());
    }
}`


public class Persons extends ArrayList<Person> {

    public void addPerson(String id, String name, int credits){
        super.add(new Person(id,name,credits));
    }

    public void sortById(){
        Collections.sort(this);
    }

    public void displayPersons() {
        for (Person p : this)
            System.out.println(p.personInfo());
    }
}


public class PersonsDemo {
    public static void main(String[] args){

        Persons persons = new Persons();
        persons.addPerson("A05","Tran Quan",7);
        persons.addPerson("A03","Nguyen An",7);
        persons.addPerson("A01","Troung Phung",5);
        persons.addPerson("A04","Phan Thi Lam",2);
        persons.addPerson("A02","Do Trung Ton",5);

        System.out.println("PERSONS UNSORTED");
        persons.displayPersons();

        System.out.println("\nPERSONS SORTED");
        persons.sortById();
        persons.displayPersons();
    }
}