如何刷新当前页面，使删除后的数据从列表框中移除？

/**
*
*/
package com;

import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

import database.OperateDB;

import entity.Grade;

/**
* @author Administrator
*
*/
public class DeleteAsGrade extends JFrame {

private static final long serialVersionUID = 1L;

private JPanel jContentPane = null;

private JLabel deleGradeLabel = null;

private JComboBox deleGradeComboBox = null;

private JButton deleSubmitButton = null;

private JButton deleCancelButton = null;

private String slectedGrade = null;

//程序图标
Image icon;

/**
* This is the default constructor
*/
public DeleteAsGrade() {
super();
initialize();
}

/**
* This method initializes this
*
* @return void
*/
private void initialize() {
this.setSize(250, 185);
this.setContentPane(getJContentPane());
this.setTitle("JFrame");
//程序图标
icon = getImage("chenggongxueyuan.jpg");
this.setIconImage(icon); //设置程序图标
}

/**
* This method initializes jContentPane
*
* @return javax.swing.JPanel
*/
private JPanel getJContentPane() {
if (jContentPane == null) {
deleGradeLabel = new JLabel();
deleGradeLabel.setBounds(new Rectangle(41, 40, 80, 20));
deleGradeLabel.setText("要删除的年级");
jContentPane = new JPanel();
jContentPane.setLayout(null);
jContentPane.add(deleGradeLabel, null);
jContentPane.add(getDeleGradeComboBox(), null);
jContentPane.add(getDeleSubmitButton(), null);
jContentPane.add(getDeleCancelButton(), null);
}
return jContentPane;
}

/**
* This method initializes deleGradeComboBox
*
* @return javax.swing.JComboBox
*/
private JComboBox getDeleGradeComboBox() {
if (deleGradeComboBox == null) {
deleGradeComboBox = new JComboBox(new String[]{"05","06","07","08","09"});
deleGradeComboBox.setBounds(new Rectangle(154, 40, 45, 20));
}
return deleGradeComboBox;

}
/**
* This method initializes deleSubmitButton
*
* @return javax.swing.JButton
*/
private JButton getDeleSubmitButton() {
if (deleSubmitButton == null) {
deleSubmitButton = new JButton();
deleSubmitButton.setBounds(new Rectangle(50, 90, 60, 20));
deleSubmitButton.setText("提交");
deleSubmitButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
Grade grade = new Grade();
OperateDB operateDB = new OperateDB();
if (operateDB.deleteGrade(deleGradeComboBox.getSelectedItem().toString()) == 1)
{
JOptionPane.showMessageDialog(null, "删除成功!");
}
}
});
}
return deleSubmitButton;
}

/**
* This method initializes deleCancelButton
*
* @return javax.swing.JButton
*/
private JButton getDeleCancelButton() {
if (deleCancelButton == null) {
deleCancelButton = new JButton();
deleCancelButton.setBounds(new Rectangle(130, 90, 60, 20));
deleCancelButton.setText("取消");
deleCancelButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
deleGradeComboBox.setSelectedIndex(0);
}
});
}
return deleCancelButton;
}

/**
* 通过给定的文件名获得图像
*/
Image getImage(String filename) {
URLClassLoader urlLoader = (URLClassLoader)this.getClass().
getClassLoader();
URL url = null;
Image image = null;
url = urlLoader.findResource(filename);
image = Toolkit.getDefaultToolkit().getImage(url);
MediaTracker mediatracker = new MediaTracker(this);
try {
mediatracker.addImage(image, 0);
mediatracker.waitForID(0);
}
catch (InterruptedException _ex) {
image = null;
}
if (mediatracker.isErrorID(0)) {
image = null;
}

return image;
}


} // @jve:decl-index=0:visual-constraint="264,40"