public static void main(String[] args) throws Exception {
        // The clipboard

        final Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
        // read clipboard and take ownership to get the FlavorListener notified
        // when the content has changed but the owner has not
        processClipboard(cb);
        cb.addFlavorListener(new FlavorListener() {
            @Override
            public void flavorsChanged(FlavorEvent e) {
                processClipboard(cb);
            }
        });
        // keep thread for testing
        Thread.sleep(100000L);
    }

    public static void processClipboard(Clipboard cb) {
        // gets the content of clipboard
        Transferable trans = cb.getContents(null);
        if (trans.isDataFlavorSupported(DataFlavor.stringFlavor)) {
            try {
                // cast to string
                String s = (String) trans
                        .getTransferData(DataFlavor.stringFlavor);
                System.out.println(s);
                // only StringSelection can take ownership, i think
                StringSelection ss = new StringSelection(s);
                // set content, take ownership
                cb.setContents(ss, ss);
            } catch (UnsupportedFlavorException e2) {
                e2.printStackTrace();
            } catch (IOException e2) {
                e2.printStackTrace();
            }
        }
    }