java中三个按钮共享一个监听器，但我的程序编译不了，高手帮我看看吧

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

import java.util.*;
public class ButtonTest
{
public static void main(String[] args)
{
ButtonFrame frame=new ButtonFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
class ButtonFrame extends JFrame
{
public ButtonFrame()
{
setTitle("ButtonTest");
setBounds(100,100,300,200);
ButtonPanel panel=new ButtonPanel();
add(panel);
}
}
/**********
class ButtonPanel extends JPanel
{
public ButtonPanel()
{
JButton yellowButton=new JButton("yellow");
JButton blueButton=new JButton("blue");
JButton redButton=new JButton("red");

add(yellowButton);
add(blueButton);
add(redButton);

//********为每个颜色构造一个对象，并将这些对象设置为按钮监听器***
ColorAction yellowAction=new ColorAction(Color.YELLOW);
ColorAction blueAction=new ColorAction(Color.BLUE);
ColorAction redAction=new ColorAction(Color.RED);

yellowButton.addActionListener(yellowAction);//为事件源添加监听器对象
blueButton.addActionListener(blueAction);
redButton.addActionListener(redAction);
}

class ColorAction implements ActionListener
{
public ColorAction(Color c)
{
backgroundColor=c;
} 
public void actionPerformed(ActionEvent event)
{
setBackground(backgroundColor);
}
Color backgroundColor;
}
//Color backgroundColor;
}
*************/
class ButtonPanel extends JPanel implements ActionListener
{

public ButtonPanel()
{

JButton yellowButton=new JButton("yellow");
JButton blueButton=new JButton("blue");
JButton redButton=new JButton("red");

add(yellowButton);
add(blueButton);
add(redButton);

yellowButton.addActionListener(this);
blueButton.addActionListener(this);
redButton.addActionListener(this);
}

public void actionPerformed(ActionEvent event)
{
JButton bt=(JButton) event.getSource(); 
if(bt==yellowButton)
setBackground(Color.YELLOW);
else if(bt==blueButton)
setBackground(Color.BLUE);
else if(bt==redButton)
setBackground(Color.RED);

}
}
  java，监听器， --------------------编程问答-------------------- 格式复制过来，就不好看了，大家见谅呀 --------------------编程问答-------------------- --------------------编程问答-------------------- 建议楼主调好格式，去javase板块里发帖子 --------------------编程问答--------------------

import java.awt.Color;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;



import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;



public class ButtonTest

{

    public static void main(String[] args)

    {

        ButtonFrame frame = new ButtonFrame();

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setVisible(true);

    }

}



class ButtonFrame extends JFrame

{

    public ButtonFrame()

    {

        setTitle("ButtonTest");

        setBounds(100, 100, 300, 200);

        ButtonPanel panel = new ButtonPanel();

        add(panel);

    }

}



class ButtonPanel extends JPanel implements ActionListener

{

    private String CMD_YELLOW = "yellow";

    private String CMD_BLUE = "blue";

    private String CMD_RED = "red";

    public ButtonPanel()

    {



        JButton yellowButton = new JButton(CMD_YELLOW);

        JButton blueButton = new JButton(CMD_BLUE);

        JButton redButton = new JButton(CMD_RED);



        add(yellowButton);

        add(blueButton);

        add(redButton);



        yellowButton.addActionListener(this);

        blueButton.addActionListener(this);

        redButton.addActionListener(this);

    }



    public void actionPerformed(ActionEvent e)

    {

        if (CMD_YELLOW.equals(e.getActionCommand()))

        {

            setBackground(Color.YELLOW);            

        }

        else if (CMD_BLUE.equals(e.getActionCommand()))

        {

            setBackground(Color.BLUE);            

        }   else if (CMD_RED.equals(e.getActionCommand()))

            setBackground(Color.RED);



    }

}

补充：Java ,  非技术区