public final class Snippet {

    /**
     * Default constructor.
     */
    private Snippet() {
    }

    /**
     * The number of line to display.
     */
    private static final int LINE_LIMIT = 10;

    /**
     * The shell.
     */
    private static Shell shell;

    /**
     * The timer to use.
     */
    private static Timer timer;

    /**
     * The number of iteration past the 10 first.
     */
    private static int loop;

    /**
     * @param args the program arguments.
     */
    public static void main(final String[] args) {
        Display display = new Display();
        shell = new Shell(display);
        shell.setText("TextViewer ex");
        shell.setLayout(new FillLayout());
        final int width = 175;
        final int height = 200;
        shell.setSize(width, height);
        timer = new Timer();
        loop = 0;
        createContents();
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
        timer.cancel();
    }

    /**
     * Create the contents.
     */
    private static void createContents() {
        Composite comp = new Composite(shell, SWT.None);
        comp.setLayout(new GridLayout(1, false));
        final TextViewer textViewer =
            new TextViewer(comp, SWT.MULTI | SWT.V_SCROLL);

        final Document document = new Document();
        document.set("Initial text\n");
        textViewer.setDocument(document);
        textViewer.getControl().setLayoutData(
            new GridData(SWT.FILL, SWT.FILL, true, true));

        TimerTask task = new TimerTask() {

            /**
             * {@inheritDoc}
             */
            @Override
            public void run() {
                final int numberOfLine = document.getNumberOfLines();
                int currentNumberOfLine = numberOfLine;
                if (LINE_LIMIT < numberOfLine) {
                    if (shell != null && !shell.isDisposed()) {
                        shell.getDisplay().asyncExec(new Runnable() {

                            public void run() {
                                try {
                                    final IRegion region =
                                        document.getLineInformation(0);
                                    document.replace(0, region.getLength() + 1,
                                        "");
                                } catch (BadLocationException e) {
                                    e.printStackTrace();
                                }
                            }
                        });
                    }
                    currentNumberOfLine--;
                    loop++;
                }
                if (shell != null && !shell.isDisposed()) {
                    final int realNumberOfLine = currentNumberOfLine;
                    shell.getDisplay().asyncExec(new Runnable() {

                        /**
                         * {@inheritDoc}
                         */
                        public void run() {
                            try {
                                IRegion info =
                                    document
                                        .getLineInformation(realNumberOfLine - 1);
                                String text = "Occurence {0} {1} {2}\n";
                                String separator = "";
                                String index = "";
                                if (loop > 0) {
                                    separator = "-";
                                    index = "" + loop;
                                }
                                document.replace(info.getOffset()
                                    + info.getLength(), 0, MessageFormat
                                    .format(text, realNumberOfLine, separator,
                                        index));
                                if (textViewer.getControl() != null
                                    && !textViewer.getControl().isDisposed()) {
                                    textViewer.refresh();
                                }
                            } catch (BadLocationException e) {
                                e.printStackTrace();
                            }
                        };
                    });
                }
            }
        };
        final long period = 500L;
        timer.scheduleAtFixedRate(task, 0L, period);
    }

}