https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#sort(java.util.List)

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
 
 
/**
 *
 * @author bogusz.thierry
 */
public class JavaApplication1 {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
 
        ArrayList<Note> lesNotes = new ArrayList();
 
        lesNotes.add ( new Note ( "Pasqualini", 18));
        lesNotes.add ( new Note ( "Bourgeois", 19));
        lesNotes.add ( new Note ( "Techer", 15));
        lesNotes.add ( new Note ( "Bogusz", 17));
 
        // Tri sur la note "à la demande"
        Collections.sort ( lesNotes,
        new Comparator<Note>(){        
        public int compare (Note n1, Note n2){
            if (n1.note ==  n2.note) return 0;
            if (n1.note > n2.note) return 1;
            return -1;
        }
        });
 
        System.out.println("----Trie sur la note----");
        for ( Note n : lesNotes ){
            System.out.println (n.nom + ":" +  n.note);
        }
 
        // Tri sur le nom implémenter dans Note
        Collections.sort ( lesNotes );
        System.out.println("----Trie sur le nom----");
        for ( Note n : lesNotes ){
            System.out.println (n.nom + ":" +  n.note);
        }
    }
 
}
 
class Note implements Comparable<Note>{
    public String nom;
    public int note;
 
    public Note ( String nom, int note){
        this.nom = nom;
        this.note = note;
    }
 
    public int compareTo ( Note autreNote){
        return nom.compareTo(autreNote.nom);
    }
}