Make sure that my JTextField has the focus when a JFrame is created in Java

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
/*from  w w w  . j  a v  a2  s  .c om*/
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Main extends JFrame {
  JTextField field1 = new JTextField(10);;
  JTextField field2 = new JTextField(10);;
  JPanel panel = new JPanel();
  public Main() {
    panel.add(new JLabel("Field 1:"));
    panel.add(field1);
    panel.add(new JLabel("Field 2:"));
    panel.add(field2);

    getContentPane().add("Center", panel);

    addWindowListener(new WindowAdapter() {
      public void windowOpened(WindowEvent e) {
        field1.requestFocus();
      }
    });

    pack();
    setVisible(true);
  }
  public static void main(String[] argv) {
    new Main();
  }
}