一个JAVA的问题(菜鸟问题)

我在用swing界面做一个登录框,但出现如下问题:

我有下拉框One 和Two.
One 下拉框里的值有"a和b",two下拉框要对应的是"aaa"和"bbb",

我想要的效果是选择one下拉框a时,,two下拉框显示aaa;
one下拉框为b时,two下拉框为bbb,

用什么样的方法可以实现,,那个if判断我已经做了,出现的问题是,我必须得选择one下拉框,然后点击确定,two下拉框才能显示相应的值..

有什么的方法可以直接判断one的值来显示two里的值..

以下是我的部分代码:
void setPower() {
if (cboPower.getSelectedItem().equals("超级管理员")) {
dbUser = new DBUserInfo();
ArrayList list = dbUser.select(1);
for (int i = 0; i < list.size(); i++) {
cboName.addItem(list.get(i));
}
}
if (cboPower.getSelectedItem().equals("管理员")) {
dbUser = new DBUserInfo();
ArrayList list = dbUser.select(2);
for (int i = 0; i < list.size(); i++) {
cboName.addItem(list.get(i));
}
}

给你一个我曾经写过的例子：

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ComboBoxDemo extends JFrame implements ActionListener {

private DefaultComboBoxModel model = new DefaultComboBoxModel();

private DefaultComboBoxModel model1 = new DefaultComboBoxModel();

private JComboBox firstComboBox;

private JComboBox secondComboBox;

private String[] first = { "101", "102", "103" };

private String[] second_first = { "10101", "10102", "10103" };

private String[] second_second = { "10201", "10202", "10203" };

private String[] second_third = { "10301", "10302", "10303" };