Java Swing ListDataListener implement

import java.awt.BorderLayout;

import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.event.ListDataEvent;
import javax.swing.event.ListDataListener;

class MyListDataListener implements ListDataListener {
  public void contentsChanged(ListDataEvent e) {
      System.out.println("contentsChanged: " + e.getIndex0() +
                 ", " + e.getIndex1()); 
  }//  w ww  .j  a  v  a  2s. c  o m
  public void intervalAdded(ListDataEvent e) {
    System.out.println("intervalAdded: " + e.getIndex0() +
                 ", " + e.getIndex1()); 
  }
  public void intervalRemoved(ListDataEvent e) {
    System.out.println("intervalRemoved: " + e.getIndex0() +
                 ", " + e.getIndex1()); 
  }
}


public class Main {
  static String labels[] = { "A", "B", "C", "D", "E", "F", "G" };

  public static void main(String args[]) {
    JFrame frame = new JFrame("Modifying Model");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    DefaultListModel<String> model = new DefaultListModel<>();
    model.addElement("CSS");
    model.addElement("HTML");
    model.addElement("Java");

    model.addListDataListener(new MyListDataListener());
    JList<String> jlist = new JList<>(model);
    
    JScrollPane scrollPane1 = new JScrollPane(jlist);
    frame.add(scrollPane1, BorderLayout.CENTER);

    frame.setSize(640, 300);
    frame.setVisible(true);
  }
}