private void initPanel(){
        panel.setBackground(Color.black);
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        panel.add(Box.createRigidArea(new Dimension(30, 50)));
        panel.add(label);
        panel.add(Box.createRigidArea(new Dimension(30, 50)));
        panel.addKeyListener(new KeyListener() {

            @Override
            public void keyTyped(KeyEvent e) {
            }

            @Override
            public void keyReleased(KeyEvent e) {
            }

            @Override
            public void keyPressed(KeyEvent e) {

                if (sb.length() <= MAX_LENGTH) {
                    if (String.valueOf(e.getKeyChar()).matches("[a-zA-Z0-9]")) {
                        sb.append(e.getKeyChar());
                    }
                }
                label.setText(sb.toString());

                if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                    quit();
                }
                if (e.getKeyCode() == KeyEvent.VK_BACK_SPACE) {
                    if (sb.length() > 0) {
                        sb.deleteCharAt(sb.length() - 1);
                        label.setText(sb.toString());
                    }

                }

            }
        });
        panel.setFocusable(true);
    }