Java Tutorial/Swing Event/PropertyChangeListener

Listening to Component Events with a PropertyChangeListener

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.Action;
import javax.swing.Icon;
import javax.swing.JButton;
import javax.swing.JFrame;
class ActionChangedListener implements PropertyChangeListener {
  private JButton button;
  public ActionChangedListener(JButton button) {
    this.button = button;
  }
  public void propertyChange(PropertyChangeEvent e) {
    String propertyName = e.getPropertyName();
    System.out.println(propertyName);
    if (e.getPropertyName().equals(Action.NAME)) {
      String text = (String) e.getNewValue();
      button.setText(text);
      button.repaint();
    } else if (propertyName.equals("enabled")) {
      Boolean enabledState = (Boolean) e.getNewValue();
      button.setEnabled(enabledState.booleanValue());
      button.repaint();
    } else if (e.getPropertyName().equals(Action.SMALL_ICON)) {
      Icon icon = (Icon) e.getNewValue();
      button.setIcon(icon);
      button.invalidate();
      button.repaint();
    }
  }
}
public class PropertyListenerJComponent {
  public static void main(String[] a) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JButton bn = new JButton();
    bn.addPropertyChangeListener(new ActionChangedListener(bn));
    frame.add(bn);
    bn.setEnabled(false);
    frame.setSize(300, 300);
    frame.setVisible(true);
    frame.add(bn);
  }
}