Java SE (3) 之 事件监听

package com.sun;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Demo_1_1 extends JFrame implements ActionListener{

    Mypanel mp;
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Demo_1_1  demo1 = new Demo_1_1();
        
    }
    public Demo_1_1() {
         mp = new Mypanel();
        JButton jb1 = new JButton("Button");
        JButton jb2 = new JButton("Button2");
        jb1.addActionListener(this);
        jb1.setActionCommand("kaishi");
        jb2.addActionListener(this);
        jb2.setActionCommand("jieshu");
        this.add(mp);
        this.add(jb1,BorderLayout.EAST);
        this.add(jb2,BorderLayout.NORTH);
        // TODO Auto-generated constructor stub
        this.setTitle("demo");
        this.setSize(300,300);
        this.setLocation(40, 40);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setVisible(true);
    }
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
        if(e.getActionCommand().equals("kaishi")){
              System.out.println("this is yes ");
              mp.setBackground(Color.BLUE);
            
        }else if(e.getActionCommand().equals("jieshu")) {
             System.out.println("this is no ");
             mp.setBackground(Color.BLACK);
        }
    }
}
class Mypanel extends JPanel{
    
    public void paint(Graphics g){        
        super.paint(g);
            g.fillRect(0, 0, 300, 300);
            g.setColor(Color.YELLOW);
            g.fillRect(40, 40, 50, 50);
    }
}