Java JFrame handle window event

import java.awt.FlowLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;

public class Main extends JFrame {
  public Main() {
    super("JButton");

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLayout(new FlowLayout());

    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.out.println("about to close");
      }//from  ww  w .  j a  v a  2  s. co  m
    });
  }

  public static void main(String[] args) {
    Main frame = new Main();
    frame.pack();
    frame.setVisible(true);
  }
}