我的(Java/Swing)MouseListener没有听,请帮我搞清楚原因

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

public class MouseListenerExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Mouse Listener Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);

        JButton button = new JButton("Click me!");
        button.addMouseListener(new MyMouseListener());

        frame.getContentPane().add(button);
        frame.setVisible(true);
    }
}

class MyMouseListener implements MouseListener {
    public void mouseClicked(MouseEvent e) {
        System.out.println("Mouse clicked!");
    }

    public void mousePressed(MouseEvent e) {
        System.out.println("Mouse pressed!");
    }

    public void mouseReleased(MouseEvent e) {
        System.out.println("Mouse released!");
    }

    public void mouseEntered(MouseEvent e) {
        System.out.println("Mouse entered!");
    }

    public void mouseExited(MouseEvent e) {
        System.out.println("Mouse exited!");
    }
}