为选择框添加事件

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//ComboBox.java
//为选择框添加事件
//2009-11-19

//<applet code=ComboBox1 width=200 height=100>
//</applet>

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

public class ComboBox1 extends JApplet
{
String[] choiceItem={"choice1","choice2","choice3","choice4"};
JComboBox box=new JComboBox(choiceItem);
JTextField txt1=new JTextField(15);
JTextArea txt2=new JTextArea(15,15);

class ActionLis implements ActionListener
{
  public void actionPerformed(ActionEvent e){
   txt1.setText("index"+box.getSelectedIndex()+":"+
    ((JComboBox)e.getSource()).getSelectedItem());
  }
}

class ItemLis implements ItemListener
{
  public void itemStateChanged(ItemEvent e){
   txt2.append(e.paramString()+"/n");
  }
}

public void init(){
  Container cp=getContentPane();
  cp.setLayout(new FlowLayout());
  cp.add(box);
  cp.add(txt1);
  cp.add(new JScrollPane(txt2));

box.addActionListener(new ActionLis());
box.addItemListener(new ItemLis());
}
}