请帮忙看下代码，连接数据库的课程设计，有错误改不过来，速求！！！
package 界面设计;import java.awt.Button;
public class Student extends JFrame {
public Student() {
}
JMenuBar menubar;//菜单栏
JMenu menu1,menu2,menu3;
JMenuItem itme1,item2,item3;
ImageIcon background;
JTextArea jt;
final Container con=this.getContentPane();
/**
* @wbp.nonvisual location=160,-13
*/
private final Panel panel = new Panel();
private JMenuItem menuItem;
private JMenuItem menuItem_1;
private JMenuItem menuItem_2;
private User user;
public void StudentShow(User user2) {
// TODO Auto-generated method stub
this.user=user2;
init();
}
public void init(){
// TODO Auto-generated method stub
this.user=user;
JLabel lab;
this.setTitle("一般用户界面--张愉");
//背景图片
background = new ImageIcon("t.png");
// 把背景图片显示在一个标签里面
lab = new JLabel(background);
// 把标签的大小位置设置为图片刚好填充整个面板
lab.setBounds(0, 0, background.getIconWidth(), background.getIconHeight());
// 把内容窗格转化为JPanel，否则不能用方法setOpaque()来使内容窗格透明
JPanel imagePanel = (JPanel) this.getContentPane();
getContentPane().setLayout(new CardLayout(0, 0));
imagePanel.setOpaque(false);
// 把背景图片添加到分层窗格的最底层作为背景
this.getLayeredPane().add(lab, new Integer(Integer.MIN_VALUE));
menubar=new JMenuBar();
this.setJMenuBar(menubar);
menubar.setBackground(Color.gray);
menu1=new JMenu("信息维护");
menu2=new JMenu("\u6210\u7EE9\u67E5\u8BE2");//成绩查询菜单
menu3=new JMenu("课程查询");
itme1=new JMenuItem("信息更新");
menu1.add(itme1);
menubar.add(menu1);
menubar.add(menu2);
//按班级查询成绩
menuItem = new JMenuItem("\u6309\u73ED\u7EA7\u67E5\u8BE2");
menuItem.addActionListener(new ActionListener() {
JLabel[] lab=new JLabel[9];
JTextField[] txt=new JTextField[6];
Button bt1,bt2;
public void actionPerformed(ActionEvent e) {
con.removeAll();
JPanel jp=new JPanel();
jp.setLayout(new BorderLayout());
jp.setOpaque(false);
JPanel jp1=new JPanel();
jp1.setLayout(new GridLayout(10,1));
jp1.setOpaque(false);
lab[0]=new JLabel("按班级查询:");
lab[0].setFont(new Font("隶书",0,30));
lab[0].setForeground(Color.green);
String s[]={"20060101","20070101","20070201","20070301","20070302","20070303","20070304",
"20070305","20070306","20070307","20070501","20070502","20070503","20070504"};
JComboBox jc1=new JComboBox(s);
lab[1]=new JLabel("按课程查询:");
lab[1].setFont(new Font("隶书",0,30));
lab[1].setForeground(Color.green);
String s1[]={"DB_大学s英语","高等数学","思想品德教育","法律基础","电工基础","电子技术基础","电子线路基础",
"计算机文化基础","C语言程序设计与数据结构","软件工程","JAVA程序设计基础","JAVA高级程序设计","数据库原理及应用",
"计算机网络技术","网页制作技术","JAVA项目实训","JSP程序设计","计算机组装与维修"};
JComboBox jc2=new JComboBox(s1);
lab[2]=new JLabel("按专业查询:");
lab[2].setFont(new Font("隶书",0,30));
lab[2].setForeground(Color.green);
String s2[]={"电子工程专业","计算机工程专业","航空专业","金融专业","软件工程专业"};
JComboBox jc3=new JComboBox(s2);
jc3.setEnabled(false);
JPanel jp2=new JPanel();
jp2.setLayout(new FlowLayout(FlowLayout.LEFT));
jp2.setOpaque(false);
bt1=new Button("查询");
bt2=new Button("取消");
jp2.add(bt1);
jp2.add(bt2);
jp1.add(lab[0]);
jp1.add(jc1);
jp1.add(lab[1]);
jp1.add(jc2);
jp1.add(lab[2]);
jp1.add(jc3);
jp1.add(jp2);
jp.add("West",jp1);
con.add(jp);
con.repaint();
con.validate();
}
});
menu2.add(menuItem);
menuItem_1 = new JMenuItem("\u6309\u8BFE\u7A0B\u67E5\u8BE2");
menu2.add(menuItem_1);
menuItem_2 = new JMenuItem("\u6309\u4E13\u4E1A\u67E5\u8BE2");
menu2.add(menuItem_2);
menubar.add(menu3);
//信息更新页面
itme1.addActionListener(new ActionListener(){
JLabel[] lab=new JLabel[9];
JTextField[] txt=new JTextField[6];
Button bt1,bt2;
User user1;
UserDao userdao=new UserImplement();
@Override
public void actionPerformed(ActionEvent e) {
user1=userdao.SgetUser(user.getId());
//user1==null,说明在student表中没有次学生的xin'xi
if(user1==null){
Show(null,null,null);
}
else{
//班级，学号，班级编号
String str1,str2,str3;
str1=user1.getClassName();
str2=user1.getId();
str3=user1.getNumber();
Show(str1,str2,str3);
}
}
private void Show(String s1,String s2,String s3) {
final String str1=s1;
final String str2=s2;
final String str3=s3;
boolean flage=false;
con.removeAll();
JPanel jp=new JPanel();
jp.setOpaque(false);
jp.setLayout(null);
lab[1]=new JLabel("姓名:");
txt[0]=new JTextField();
txt[0].setText(user.getName());
txt[0].setEditable(flage);
txt[0].setBounds(130, 38, 100, 25);
lab[1].setFont(new Font("隶书",0,30));
lab[1].setForeground(Color.green);
lab[1].setBounds(50,-50, 200, 200);
jp.add(lab[1]);
jp.add(txt[0]);
lab[2]=new JLabel("性别:");
txt[1]=new JTextField();
txt[1].setText(user.getSex());
txt[1].setEditable(flage);
txt[1].setBounds(410, 38, 100, 25);
lab[2].setFont(new Font("隶书",0,30));
lab[2].setForeground(Color.green);
lab[2].setBounds(330,-50, 200, 200);
jp.add(lab[2]);
jp.add(txt[1]);
lab[3]=new JLabel("出生日期:");
txt[2]=new JTextField();
txt[2].setEditable(flage);
txt[2].setText(user.getBrithday()+"");
txt[2].setBounds(710, 38, 100, 25);
lab[3].setFont(new Font("隶书",0,30));
lab[3].setForeground(Color.green);
lab[3].setBounds(570,-50, 200, 200);
jp.add(lab[3]);
jp.add(txt[2]);
lab[4]=new JLabel("班级:");
txt[3]=new JTextField();
txt[3].setEditable(flage);
txt[3].setText(str1);//班级名
txt[3].setBounds(130, 138, 100, 25);
lab[4].setFont(new Font("隶书",0,30));
lab[4].setForeground(Color.green);
lab[4].setBounds(50,50, 200, 200);
jp.add(lab[4]);
jp.add(txt[3]);
lab[5]=new JLabel("学号:");
txt[4]=new JTextField();
txt[4].setEditable(false);
txt[4].setText(str2);//学号
txt[4].setBounds(410, 138, 100, 25);
lab[5].setFont(new Font("隶书",0,30));
lab[5].setForeground(Color.green);
lab[5].setBounds(330,50, 200, 200);
jp.add(lab[5]);
jp.add(txt[4]);
lab[6]=new JLabel("班级编号:");
txt[5]=new JTextField();
txt[5].setEditable(flage);
txt[5].setText(str3);//班级班号
txt[5].setBounds(710, 138, 100, 25);
lab[6].setFont(new Font("隶书",0,30));
lab[6].setForeground(Color.green);
lab[6].setBounds(570,50, 200, 200);
jp.add(lab[6]);
jp.add(txt[5]);
lab[7]=new JLabel("简介:");
lab[7].setFont(new Font("隶书",0,30));
lab[7].setForeground(Color.green);
lab[7].setBounds(50, 130, 200, 200);
jt=new JTextArea();
jt.setEditable(flage);
jt.setBackground(Color.darkGray);
jt.setForeground(Color.white);
jt.setFont(new Font("隶书",0,30));
jt.setBounds(50,250,770,160);
jp.add(lab[7]);
jp.add(jt);
bt1=new Button("保存");
bt1.setBounds(300,420, 50, 30);
bt1.setBackground(Color.green);
bt2=new Button("编辑");
bt2.setBounds(400,420, 50, 30);
bt2.setBackground(Color.green);
jp.add(bt1);
jp.add(bt2);
//保存按钮的事件监听器
// bt1.addActionListener(new ActionListener(){
// User user2;
// @Override
// public void actionPerformed(ActionEvent e) {
// // TODO Auto-generated method stub
// System.out.println("进去了");
// UserDao userdao=new UserImplement();
// user2=userdao.SgetUser(user.getId());
// if(user!=null){
// System.out.println("hao"+user2.getId());
// user2.setId(user.getId());
// user2.setName(txt[0].getText());
// user2.setSex(txt[1].getText());
// user2.setNumber(txt[5].getText());
// System.out.println(txt[5].getText());
// userdao.update(user2);
// }
//
// }
//
// });
//编辑按钮添加事件监听器
bt2.addActionListener(new ActionListener(){
boolean flage=true;
public void actionPerformed(ActionEvent e) {
con.removeAll();
JPanel jp=new JPanel();
jp.setOpaque(false);
jp.setLayout(null);
lab[1]=new JLabel("姓名:");
txt[0]=new JTextField();
txt[0].setText(user.getName());
txt[0].setEditable(flage);
txt[0].setBounds(130, 38, 100, 25);
lab[1].setFont(new Font("隶书",0,30));
lab[1].setForeground(Color.green);
lab[1].setBounds(50,-50, 200, 200);
jp.add(lab[1]);
jp.add(txt[0]);
lab[2]=new JLabel("性别:");
txt[1]=new JTextField();
txt[1].setText(user.getSex());
txt[1].setEditable(flage);
txt[1].setBounds(410, 38, 100, 25);
lab[2].setFont(new Font("隶书",0,30));
lab[2].setForeground(Color.green);
lab[2].setBounds(330,-50, 200, 200);
jp.add(lab[2]);
jp.add(txt[1]);
lab[3]=new JLabel("出生日期:");
txt[2]=new JTextField();
txt[2].setEditable(flage);
txt[2].setText(user.getBrithday()+"");
txt[2].setBounds(710, 38, 100, 25);
lab[3].setFont(new Font("隶书",0,30));
lab[3].setForeground(Color.green);
lab[3].setBounds(570,-50, 200, 200);
jp.add(lab[3]);
jp.add(txt[2]);
lab[4]=new JLabel("班级:");
txt[3]=new JTextField();
txt[3].setText(str1);//班级名
txt[3].setBounds(130, 138, 100, 25);
lab[4].setFont(new Font("隶书",0,30));
lab[4].setForeground(Color.green);
lab[4].setBounds(50,50, 200, 200);
jp.add(lab[4]);
jp.add(txt[3]);
lab[5]=new JLabel("学号:");
txt[4]=new JTextField();
txt[4].setEditable(flage);
txt[4].setText(str2);//学号
txt[4].setBounds(410, 138, 100, 25);
lab[5].setFont(new Font("隶书",0,30));
lab[5].setForeground(Color.green);
lab[5].setBounds(330,50, 200, 200);
jp.add(lab[5]);
jp.add(txt[4]);
lab[6]=new JLabel("班级编号:");
txt[5]=new JTextField();
txt[5].setEditable(flage);
txt[5].setText(str3);//班级班号
txt[5].setBounds(710, 138, 100, 25);
lab[6].setFont(new Font("隶书",0,30));
lab[6].setForeground(Color.green);
lab[6].setBounds(570,50, 200, 200);
jp.add(lab[6]);
jp.add(txt[5]);
lab[7]=new JLabel("简介:");
lab[7].setFont(new Font("隶书",0,30));
lab[7].setForeground(Color.green);
lab[7].setBounds(50, 130, 200, 200);
jt=new JTextArea();
jt.setEditable(flage);
jt.setBackground(Color.darkGray);
jt.setForeground(Color.white);
jt.setFont(new Font("隶书",0,30));
jt.setBounds(50,250,770,160);
jp.add(lab[7]);
jp.add(jt);
bt1=new Button("保存");
bt1.setBounds(300,420, 50, 30);
bt1.setBackground(Color.green);
bt2=new Button("编辑");
bt2.setBounds(400,420, 50, 30);
bt2.setBackground(Color.green);
jp.add(bt1);
jp.add(bt2);
//保存按钮的事件监听器
bt1.addActionListener(new ActionListener(){
User user2;
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
UserDao userdao=new UserImplement();
user2=userdao.SgetUser(user.getId());
if(user2!=null){
save();
userdao.update(user2);
}
else{
System.out.println("1进去了");
System.out.println("hao"+user.getId());
System.out.println(txt[5].getText());
save();//弟423
}
}
public void save(){
user2.setId(user.getId());//弟427行
user2.setName(txt[0].getText());
user2.setSex(txt[1].getText());
user2.setNumber(txt[5].getText());
}
});
con.add(jp);
con.repaint();
con.validate();
}
});
con.add(jp);
con.repaint();
con.validate();
}
});
this.setBounds(300, 100, 843,525);
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
}
}
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at 界面设计.Student$2$1$1.save(Student.java:427)
at 界面设计.Student$2$1$1.actionPerformed(Student.java:423)
at java.awt.Button.processActionEvent(Button.java:409)
at java.awt.Button.processEvent(Button.java:377)
at java.(Component.java:4861)
at java.(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
请帮忙看下，做课程设计连接数据库方面，许多代码没有优化都是临时起意，速求！！！
