document.addDocumentListener(new ScrollDocumentToEnd(textArea));
JScrollPane scrollPane = new JScrollPane(textArea);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setPreferredSize(new Dimension(300, 100));
scrollPane.addKeyListener(handler);
panel.add(scrollPane, BorderLayout.SOUTH);
frame.getContentPane().add(panel);
frame.pack();
frame.setVisible(true);