java Checkbox中出现if语句 例如checkbox为true textfield就输出A

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

public class ww implements ItemListener
{
TextField tf1,tf2;
Checkbox cb1,cb2;
public static void main(String agrs[]){

ww aa=new ww();
aa.go();
}
public void go()
{
Frame f=new Frame("JAVA");
f.setSize(200,200);
f.setVisible(true);
f.setLayout(new FlowLayout());
tf1=new TextField(10);
tf2=new TextField(10);
cb1=new Checkbox("A选框",true);
cb2=new Checkbox("B选框",false);
f.add(tf1);
f.add(tf2);
f.add(cb1);
f.add(cb2);
cb1.addItemListener(this);
cb2.addItemListener(this);
}
public void itemStateChanged(ItemEvent e)
{
if(e.getSource()==cb1);
{
if(cb1.getState()==true)
{String s1="选框A选中";
tf1.setText(s1);}

else
{String s2