I used a TreeSet model to get a sorted JList but it isn't sorted.

[eLancaster]

I implemented an AbstractListModel using a sorted set in order to make a JList, but when i run the program, the list is unsorted. What am I doing wrong?

SortedListModel.java

import java.util.Collection;
import java.util.Iterator;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.Arrays;

import javax.swing.AbstractListModel;


public class SortedListModel extends AbstractListModel {

	SortedSet listModel;
	
	public SortedListModel()
	{
		listModel = new TreeSet();
	}
	
	public Object getElementAt(int index) {
		return listModel.toArray()[index];
	}
	
	public int getSize() {
		return listModel.size();
	}
	
	public void addAll(Object elements[])
	{
		Collection c  = Arrays.asList(elements);
		listModel.addAll(c);
		fireContentsChanged(this,0,getSize());
	}
	
	public void clear()
	{
		listModel.clear();
		fireContentsChanged(this,0,getSize());
	}
	
	public boolean contains(Object element)
	{
		return listModel.contains(element);
	}
	
	public Object firstElement()
	{
		return listModel.first();
	}
	
	public Object lastElement()
	{
		return listModel.last();
	}
	
	public Iterator iterator()
	{
		return listModel.iterator();
	}
	
	public boolean removeElement(Object element)
	{
		boolean removed = listModel.remove(element);
		if(removed)
		{
			fireContentsChanged(this,0,getSize());
		}
		return removed;
	}

}

ContactList.java

import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.List;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;


public class ContactList {
	private JFrame window;
	private JList contactList;
	private ArrayList<Person> people;
	private JTextField nameField;
	private JTextField ageField;
	private JButton addNewPerson;
	
	public ContactList()
	{
		createContactList();
		createUI();
	}
	
	private void createUI()
	{
		window = new JFrame();
		window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		window.setVisible(true);
		window.setSize(new Dimension(300,500));
		
		SortedListModel model = new SortedListModel();
		contactList = new JList(model);
		updateList();
		contactList.setVisibleRowCount(4);
		
		nameField = new JTextField(10);
		
		ageField = new JTextField(3);
		
		addNewPerson = new JButton("+");
		addNewPerson.addActionListener(new ActionListener(){
			public void actionPerformed(ActionEvent event)
			{
				Person p = new Person(nameField.getText(),Integer.parseInt(ageField.getText()));
				people.add(p);
				updateList();
			}
		});
		
		
		Container panel = window.getContentPane();
		panel.setLayout(new FlowLayout());
		panel.add(contactList);
		panel.add(nameField);
		panel.add(ageField);
		panel.add(addNewPerson);
	}
	
	private void updateList()
	{
		contactList.setListData(people.toArray());
	}
	
	private void createContactList()
	{
		people = new ArrayList<Person>();
		
		Person p1 = new Person("Fred",55);
		Person p2 = new Person("Ben", 24);
		Person p3 = new Person("Will", 49);
		Person p4 = new Person("Sally", 21);
		Person p5 = new Person("Sally", 21);
		
		people.add(p4);
		people.add(p3);
		people.add(p2);
		people.add(p1);
		people.add(p5);
	}
	
	public static void main(String args[])
	{
		new ContactList();
	}
}

[Tolls]

You should be putting your data into the Model not the JList.
setListData() creates a new Model for the supplied data, as per the API.