Java tutorial
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 MainClass { 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"); } } }