[java]Significato eccezione java.lang.ClassCastException

[tcc]

Cosa significa questa eccezione,generata da un cast??

java.lang.ClassCastException
	at swingtest.MenuClass.actionPerformed(MenuClass.java:97)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786)
	at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1839)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:289)
	at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1113)
	at javax.swing.plaf.basic.BasicMenuItemUI$MouseInputHandler.mouseReleased(BasicMenuItemUI.java:943)
	at java.awt.Component.processMouseEvent(Component.java:5100)
	at java.awt.Component.processEvent(Component.java:4897)
	at java.awt.Container.processEvent(Container.java:1569)
	at java.awt.Component.dispatchEventImpl(Component.java:3615)
	at java.awt.Container.dispatchEventImpl(Container.java:1627)
	at java.awt.Component.dispatchEvent(Component.java:3477)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
	at java.awt.Container.dispatchEventImpl(Container.java:1613)
	at java.awt.Window.dispatchEventImpl(Window.java:1606)
	at java.awt.Component.dispatchEvent(Component.java:3477)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
 CODICE:

public class MenuClass /*extends JDesktopPane*/ implements ActionListener{
   public JMenuBar barra = new JMenuBar();
   private JMenu file = new JMenu("File");
   private JMenu effect = new JMenu("Effect");
   private JMenuItem esci = new JMenuItem("Esci");
   private JMenuItem salva = new JMenuItem("Salva");
   private JMenuItem salvaas = new JMenuItem("Salva con nome");
   private JMenuItem apri = new JMenuItem("Apri");
   private JMenuItem inverti = new JMenuItem("Inverti");
   private JMenuItem luminosita = new JMenuItem("Luminosità");
   private JMenuItem contrasto = new JMenuItem("Contrasto");

   private JFileChooser aprifile = new JFileChooser();
   public JDesktopPane desktop = new JDesktopPane();
   public JFileChooser salvafile=new JFileChooser("C:\\Programmi");
   public JOptionPane pannellosalva = new JOptionPane();
   private JOptionPane pannello = new JOptionPane();
   public ImagePanel pannelloimmagine;
   public JInternalFrame finestra;
   public RenderedImage immagine;
   public JSlider sld;
   public JScrollPane srcimgpanel;
   public DisplayJAI srcimg;
   public OperationClass operazioni = new OperationClass();




   public MenuClass() {
     barra.add(file);
     barra.add(effect);
     file.add(apri);
     file.add(salva);
     file.add(salvaas);
     file.add(esci);
     effect.add(inverti);
     effect.add(luminosita);
     effect.add(contrasto);
     apri.addActionListener(this);
     salvaas.addActionListener(this);
     esci.addActionListener(this);
     inverti.addActionListener(this);

   }

   private String openFile(){
     aprifile.setDialogTitle("Scegli Immagine");
     aprifile.showOpenDialog (pannello);
     String fileName = new String(aprifile.getSelectedFile().toString());
     return fileName;
   }

   public void actionPerformed(ActionEvent ae) {

     if(ae.getSource() == esci){
       System.exit(0);
     }
     if(ae.getSource() == apri){
       String fileName =openFile();
       pannelloimmagine = new ImagePanel();
      finestra = pannelloimmagine.CreatePanel(fileName);
      desktop.add(finestra);

     }
     if(ae.getSource() == salvaas){
       try{
         salvafile.setDialogTitle("Inserisci percorso");
         salvafile.showSaveDialog(pannellosalva);
         String filesalvato = new String(salvafile.getSelectedFile().toString());
         JAI.create("filestore", immagine, filesalvato, "BMP", null);
       }
       catch(Exception a){
         System.out.println("Operazione annullata dall'utente");
       }
     }
    if(ae.getSource() == inverti){
      immagine = ((ImagePanel)desktop.getSelectedFrame()).getOriginalImage();
    if(immagine != null)  {
     srcimg = operazioni.Inverti(immagine);
     pannelloimmagine = new ImagePanel();
     finestra = pannelloimmagine.CreatePanel(srcimg);
     desktop.add(finestra);

       }
     else{ System.out.print("errorei invert");  }

     }


   }



 }


public class ImagePanel extends JInternalFrame
           {
     public JInternalFrame finestra,pan;
     public JScrollPane srcimgpanel;
     public DisplayJAI srcimg;
     public RenderedImage imgsrc;




     public ImagePanel() {


     }

     public JInternalFrame CreatePanel(String fileName) {
     imgsrc = JAI.create("fileload", fileName);
     finestra = new JInternalFrame(fileName, true, true, true, true);
     finestra.setSize(640,480);
     srcimgpanel = new JScrollPane();
     srcimg = new DisplayJAI(imgsrc);
     srcimgpanel.getViewport().add(srcimg);
     setPreferredSize(new Dimension(640, 480));
     finestra.getContentPane().add(srcimgpanel);
     finestra.setVisible(true);

    return finestra;
   }



   public JInternalFrame CreatePanel(DisplayJAI immagine){

       finestra = new JInternalFrame("Immagine Modificata",true,true,true,true);
       finestra.setSize(640,480);
       srcimgpanel = new JScrollPane();
       srcimgpanel.getViewport().add(immagine);
       finestra.getContentPane().add(srcimgpanel);
       finestra.setVisible(true);

       return finestra;
     }

     public RenderedImage getOriginalImage() {
       return imgsrc;
     }


}