选择JComboBox选项时，恢复难度字符串并清除txtArea

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

public class ComboBoxExample extends JFrame {
    private JComboBox<String> comboBox;
    private JTextArea txtArea;

    public ComboBoxExample() {
        setTitle("ComboBox Example");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new FlowLayout());

        // 创建一个JComboBox，并添加选项
        comboBox = new JComboBox<>();
        comboBox.addItem("简单");
        comboBox.addItem("中等");
        comboBox.addItem("困难");

        // 创建一个JTextArea用于显示难度字符串
        txtArea = new JTextArea(5, 20);
        txtArea.setEditable(false);

        // 添加JComboBox的选项监听器
        comboBox.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // 获取用户选择的选项
                String selectedDifficulty = (String) comboBox.getSelectedItem();

                // 根据选择的选项执行相应的操作
                if (selectedDifficulty.equals("简单")) {
                    txtArea.setText("您选择了简单难度");
                } else if (selectedDifficulty.equals("中等")) {
                    txtArea.setText("您选择了中等难度");
                } else if (selectedDifficulty.equals("困难")) {
                    txtArea.setText("您选择了困难难度");
                }
            }
        });

        // 添加组件到窗口中
        add(comboBox);
        add(txtArea);

        pack();
        setVisible(true);
    }

    public static void main(String[] args) {
        new ComboBoxExample();
    }
}