swing JScrollPane | Java

Question

package info.lxgg;

import java.awt.Color;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;

public class accPage implements ActionListener{
    
    static private final String newLine = "\n";
    public static String dateiname = "daten/datei.txt";
    public static String UserID;

    JFrame frame = new JFrame("Infos");
    JButton save = new JButton();
    JButton removeAll = new JButton();
    
    static JTextArea openedText = new JTextArea();

    public accPage() {
        frame.setSize(500, 500);
        frame.getContentPane().setBackground(new Color(30, 25, 25));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.setLayout(null);

        openedText.setLineWrap(true);
        openedText.setWrapStyleWord(true);
        openedText.setLayout(null);
        openedText.setBounds(0, 0, 485, 400);

        removeAll.setBounds(100, 410, 100, 40);
        removeAll.setFocusable(false);
        removeAll.setBorderPainted(false);
        removeAll.setText("REMOVE");
        removeAll.addActionListener(this);
        removeAll.setBackground(new Color(200, 200, 200));
        removeAll.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseEntered(java.awt.event.MouseEvent evt) {
                removeAll.setBackground(new Color(150, 150, 150));
            }
            public void mouseExited(java.awt.event.MouseEvent evt) {
                removeAll.setBackground(new Color(200, 200, 200));
            }
        });
        
        save.setBounds(10, 410, 80, 40);
        save.setFocusable(false);
        save.setBorderPainted(false);
        save.setText("SAVE");
        save.addActionListener(this);
        save.setBackground(new Color(200, 200, 200));
        save.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseEntered(java.awt.event.MouseEvent evt) {
                save.setBackground(new Color(150, 150, 150));
            }
            public void mouseExited(java.awt.event.MouseEvent evt) {
                save.setBackground(new Color(200, 200, 200));
            }
        });

        frame.add(removeAll);
        frame.add(save);
        frame.add(openedText);
        
        File file = new File("daten");
        File info = new File("daten/datei.txt");
        
        if(!file.exists()) {
            file.mkdirs();
        }
        
        if(!info.exists()) {
            try {
                info.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } 
        ladeDatei(dateiname);
    }
    
    public static void ladeDatei(String datName) {
        File file = new File(datName);

        if (!file.canRead() || !file.isFile())
            System.exit(0);

        FileReader fr = null;
        int c;
        StringBuffer buff = new StringBuffer();
        try {
            fr = new FileReader(file);
            while ((c = fr.read()) != -1) {
                buff.append((char) c);
            }
            fr.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        openedText.setText(buff.toString());
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == save) {
            try {
                FileWriter writer = new FileWriter(dateiname);
                writer.write(openedText.getText());
                writer.flush();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
        if(e.getSource() == removeAll) {
            try {
                FileWriter writer = new FileWriter(dateiname);
                openedText.setText("");
                writer.write(openedText.getText());
                writer.flush();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
    }
}

我想在openedText中添加一个JScrollBar，但我做不到。有人能帮我一下吗，因为我已经坐了好几个小时了，但还是拿不到

我已经用JScrollPane和JScrollBar试过了，但没有成功，所以如果有人能帮忙，我会觉得很好