如何在JTextArea中使用JMenuItems在单独的行上显示整数？

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class IntegerMenuExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("整数菜单示例");
        frame.setLayout(new BorderLayout());

        JMenuBar menuBar = new JMenuBar();
        JMenu menu = new JMenu("整数菜单");

        JMenuItem item1 = new JMenuItem("1");
        JMenuItem item2 = new JMenuItem("2");
        JMenuItem item3 = new JMenuItem("3");

        item1.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JTextArea textArea = (JTextArea) frame.getContentPane().getComponent(0);
                textArea.append(item1.getText() + "\n");
            }
        });

        item2.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JTextArea textArea = (JTextArea) frame.getContentPane().getComponent(0);
                textArea.append(item2.getText() + "\n");
            }
        });

        item3.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JTextArea textArea = (JTextArea) frame.getContentPane().getComponent(0);
                textArea.append(item3.getText() + "\n");
            }
        });

        menu.add(item1);
        menu.add(item2);
        menu.add(item3);
        menuBar.add(menu);

        frame.setJMenuBar(menuBar);

        JTextArea textArea = new JTextArea();
        textArea.setEditable(false);
        frame.add(textArea, BorderLayout.CENTER);

        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}