java 怎么把下拉列表筐的边框去掉

import java.awt.*;
import java.awt.event.*;
public class TestChoice
{
Choice ch=new Choice();
TestChoice()
{
ch.add("1");
ch.add("2");
ch.add("3");
FlowLayout fl=new FlowLayout();
Frame f=new Frame("frame");
f.setLayout(fl);
f.add(ch);
f.setBounds(0,0,200,100);
f.setVisible(true);
f.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
}
public static void main(String[] args)
{
new TestChoice();
}
}

利用CSS样式就可以解决