private void addClipListener(){
  
        /* een luisteraar definieren */
        ClipListener = new FlavorListener() {
            public void flavorsChanged(FlavorEvent e) {
                
                clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
                
                try {
                    Transferable content = clipboard.getContents(this);
                    if (content == null) {
                        System.out.println("Content is empty!");
                        return;
                    }
                    if (!content.isDataFlavorSupported(DataFlavor.stringFlavor)) {
                        System.out.println("StringFlavor not supported!");
                        return;
                    }
                    try {
                        String data = (String)content.getTransferData(DataFlavor.stringFlavor);
                        clipboard.setContents(content, new ClipboardOwner() {
                            public void lostOwnership(Clipboard clipboard, Transferable contents) {
                                String datas ="";
                                try{
                                    datas = (String)contents.getTransferData(DataFlavor.stringFlavor);
                                } catch (UnsupportedFlavorException ex) {
                                    ex.printStackTrace();
                                    System.out.println("prob1");
                                } catch (IOException ex) {
                                    ex.printStackTrace();
                                    System.out.println("prob2");
                                }
                                /* relevant data found */
                                ClipboardDataChanged(datas);
                            }
                        });
                        System.out.println("Content: \"" + data + "\"");
                    } catch (UnsupportedFlavorException ex) {
                        ex.printStackTrace();
                        System.out.println("prob1");
                    } catch (IOException ex) {
                        ex.printStackTrace();
                        System.out.println("prob2");
                    }
                } catch (IllegalStateException ex) {
                    ex.printStackTrace();
                    System.out.println("prob3");
                }
            }
        };
        
        clipboard.addFlavorListener(ClipListener);
        
    }