如何在actionPerformed方法上使TreeStructureProvider可更新？

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Observable;
import java.util.Observer;

// 实现观察者接口
class MyTreeStructureProvider extends Observable {
    public void updateTree() {
        setChanged(); // 标记为已更改
        notifyObservers(); // 通知观察者
    }
}

class MyActionListener implements ActionListener {
    private MyTreeStructureProvider treeStructureProvider;
    
    public MyActionListener(MyTreeStructureProvider treeStructureProvider) {
        this.treeStructureProvider = treeStructureProvider;
    }
    
    public void actionPerformed(ActionEvent e) {
        // 在这里进行更新操作
        treeStructureProvider.updateTree();
    }
}

class MyTreeStructureObserver implements Observer {
    public void update(Observable o, Object arg) {
        // 在这里更新树形结构
        System.out.println("树形结构已更新");
    }
}

public class Main {
    public static void main(String[] args) {
        // 创建TreeStructureProvider对象
        MyTreeStructureProvider treeStructureProvider = new MyTreeStructureProvider();
        
        // 创建观察者对象
        MyTreeStructureObserver treeStructureObserver = new MyTreeStructureObserver();
        
        // 添加观察者到TreeStructureProvider
        treeStructureProvider.addObserver(treeStructureObserver);
        
        // 创建按钮并添加动作监听器
        JButton button = new JButton("更新树形结构");
        button.addActionListener(new MyActionListener(treeStructureProvider));
        
        // 创建窗口并添加按钮
        JFrame frame = new JFrame("Tree Structure");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(button);
        frame.pack();
        frame.setVisible(true);
    }
}