private JTextArea          text;
private JScrollPane        scroll;

text = new JTextArea(15, 50);
text.setFont(new Font(Font.MONOSPACED, Font.PLAIN, text.getFont().getSize()));
text.setEditable(false);

scroll = new JScrollPane(text);
scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

public void updateText(final String value) {
    if (text != null) {
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
        Date date = new Date();

        text.append(dateFormat.format(date) + " " + value + "n");

        JScrollBar vertical = scroll.getVerticalScrollBar();
        vertical.setValue(vertical.getMaximum());
    }
}