import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class ch9_18 extends JFrame
{
    public ch9_18()
    {
        super("測(cè)試下拉列表框");
        setBounds(20,20,600,400);
        getContentPane().setLayout(null);
    }
    public static void main(String [] args)
    {
        ch9_18 f=new ch9_18();
        
        ComboBoxModel mode = new UserDefineComboBoxModel();
       
        JComboBox jcb=new JComboBox(mode);
        jcb.setBorder(BorderFactory.createTitledBorder("列表"));
        jcb.setBounds(20,20,80,50);
        
        f.getContentPane().add(jcb);
        
        f.show();
    }
}
class UserDefineComboBoxModel extends AbstractListModel implements ComboBoxModel
{
    String item=null;
    String [] s={"美國(guó)","中國(guó)","俄羅斯","日本","巴西","韓國(guó)"};
    public Object getElementAt(int index)
    {
        return s[index++];
    }
    public int getSize()
    {
        return s.length;
    }
    public void setSelectedItem(Object anItem)
    {
        item=(String)anItem;
    }
    public Object getSelectedItem()
    {
        return item;
    }
}