Java Tutorial/Swing Event/VetoableChangeListener

implements VetoableChangeListener to block focus change events

import java.awt.ruponent;
import java.awt.KeyboardFocusManager;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyVetoException;
import java.beans.VetoableChangeListener;
public class Main {
  public static void main(String[] argv) {
    KeyboardFocusManager.getCurrentKeyboardFocusManager().addVetoableChangeListener(
        new FocusVetoableChangeListener());
  }
}
class FocusVetoableChangeListener implements VetoableChangeListener {
  public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
    Component oldComp = (Component) evt.getOldValue();
    Component newComp = (Component) evt.getNewValue();
    if ("focusOwner".equals(evt.getPropertyName())) {
      if (oldComp == null) {
        System.out.println(newComp.getName());
      } else {
        System.out.println(oldComp.getName());
      }
    } else if ("focusedWindow".equals(evt.getPropertyName())) {
      if (oldComp == null) {
        System.out.println(newComp.getName());
      } else {
        System.out.println(oldComp.getName());
      }
    }
    boolean vetoFocusChange = false;
    if (vetoFocusChange) {
      throw new PropertyVetoException("message", evt);
    }
  }
}

Listening to JComponent Events with a VetoableChangeListener

import java.awt.BorderLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyVetoException;
import java.beans.VetoableChangeListener;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
public class VetoableChangeListenerDemo {
  public static void main(final String args[]) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JDesktopPane desktop = new JDesktopPane();
    JInternalFrame palette = new JInternalFrame("Palette", true, true, true, true);
    palette.addVetoableChangeListener(new IconPolice());
    palette.setBounds(350, 150, 100, 100);
    desktop.add(palette, JDesktopPane.PALETTE_LAYER);
    palette.setVisible(true);
    frame.add(desktop, BorderLayout.CENTER);
    frame.setSize(500, 300);
    frame.setVisible(true);
  }
}
class IconPolice implements VetoableChangeListener {
  public void vetoableChange(PropertyChangeEvent ev) throws PropertyVetoException {
    String name = ev.getPropertyName();
    if (name.equals(JInternalFrame.IS_ICON_PROPERTY) && (ev.getNewValue() == Boolean.TRUE)) {
      System.out.println("JInternalFrame.IS_ICON_PROPERTY");
    }
  }
}