实践证明：当类想实现两个监听接口的时候，必须把两个都设置成内部类，不可能一个是外部类实现，一个是内部类实现。这样容易捕获错误，出现异常。

最初的程序出现了错误，就是因为我把两个监听接口，一个是县委内部类，一个实现为外部类，导致监听时出现错误。把外部类屏蔽以后，内部类才可以正常工作。如下所示：

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

public class TextArea1 //implements ActionListener{
{
    JTextArea text;
    JCheckBox check;
    
    public static void main(String[] args){
        TextArea1 gui=new TextArea1();
        gui.go();
    }
    public void go(){
        JFrame frame=new JFrame();
        JPanel panel=new JPanel();
        JButton button=new JButton("Just Clicked It");
        //button.addActionListener(this);
        text=new JTextArea(10,20);
        text.setLineWrap(true);
        
        
        JScrollPane scroller=new JScrollPane(text);
        scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        
        check=new JCheckBox("Goes to 11");
        
        check.addItemListener(new CheckListener());
        
        
        panel.add(scroller);
        
        frame.getContentPane().add(BorderLayout.CENTER,panel);
        frame.getContentPane().add(BorderLayout.SOUTH,button);
        frame.getContentPane().add(BorderLayout.NORTH,check);
        
        frame.setSize(300,300);
        frame.setVisible(true);
    }
    /*public void actionPerformed(ActionEvent ev){
        text.append("button clicked 
");
    }*/
    class CheckListener implements ItemListener{
        public void itemStateChanged(ItemEvent ev){
            String onOrOff="off";
            if(check.isSelected()) onOrOff="on";
            System.out.println("Check box is "+onOrOff);
      }
    }
}

通过·设置内部类，来继承和实现ActionListener，也可以实现，程序代码如下图所示：

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

public class TextArea1 {

    JTextArea text;
    JCheckBox check;
    
    public static void main(String[] args){
        TextArea1 gui=new TextArea1();
        gui.go();
    }
    public void go(){
        JFrame frame=new JFrame();
        JPanel panel=new JPanel();
        JButton button=new JButton("Just Clicked It");
        button.addActionListener(new ButtonListener());
        text=new JTextArea(10,20);
        text.setLineWrap(true);
        
        
        JScrollPane scroller=new JScrollPane(text);
        scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        
        check=new JCheckBox("Goes to 11");
        
        check.addItemListener(new CheckListener());
        
        
        panel.add(scroller);
        
        frame.getContentPane().add(BorderLayout.CENTER,panel);
        frame.getContentPane().add(BorderLayout.SOUTH,button);
        frame.getContentPane().add(BorderLayout.NORTH,check);
        
        frame.setSize(300,300);
        frame.setVisible(true);
    }
    /*public void actionPerformed(ActionEvent ev){
        text.append("button clicked 
");
    }*/
    class ButtonListener implements ActionListener{
        public void actionPerformed(ActionEvent ev){
            text.append("button clicked 
");
        }
    }
    class CheckListener implements ItemListener{
        public void itemStateChanged(ItemEvent ev){
            String onOrOff="off";
            if(check.isSelected()) onOrOff="on";
            System.out.println("Check box is "+onOrOff);
      }
    }
}