jscrollpane卷轴仅出现在底部

Question

我有这个jframe具有jscrollpane和jtextarea ，它可以正常工作，但是滚动按钮仅出现在底部，我想要它默认显示在顶部。我该如何更改？

public class frameMyPasswords extends JFrame {

    private JPanel contentPane;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    frameMyPasswords frame = new frameMyPasswords();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public frameMyPasswords() {
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);
        
        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        //scrollPane.getViewport().setViewPosition( new Point(0, 0) );
        scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane.getVerticalScrollBar().setValue(0);
        scrollPane.setBounds(10, 45, 414, 194);
        contentPane.add(scrollPane);
        
        JTextArea txtField = new JTextArea();
        scrollPane.setViewportView(txtField);
        
        txtField.setLineWrap(true);
        txtField.setEditable(false);
        txtField.setToolTipText("");
        txtField.setText("LONG TEXT");
    }
}