求大神解决

qq_39149137 2017-12-27 10:13:09

package Main;
import ShuJuKu.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;
import java.util.*;
import java.text.*;
public class StudentAdd extends Frame{
/**
*
*/
private static final long serialVersionUID = 1L;
Label id=new Label("学生编号");
Label name=new Label("学生名字");
Label sex=new Label("学生性别");
Label age=new Label("学生年龄");
Label classNumber=new Label("学生班级号");
Label adress=new Label("学生家庭住址");
TextField idtext=new TextField();
TextField nametext=new TextField();
Choice sextext=new Choice();
TextField agetext=new TextField();
TextField classNumbertext=new TextField();
TextField adresstext=new TextField();
Button BaoCun=new Button("保存");
Button quit=new Button("退出");
StudentAdd(){
setLayout(null);
setTitle("学生添加");
setSize(500,300);
id.setBounds(30, 80, 50, 15);
idtext.setBounds(110, 80, 100, 20);
name.setBounds(280, 80, 50, 15);
nametext.setBounds(360, 80, 100, 20);
sex.setBounds(30, 130, 50, 15);
sextext.setBounds(110, 130, 80, 20);
sextext.add("男");
sextext.add("女");
age.setBounds(280, 130, 50, 15);
agetext.setBounds(360, 130, 100, 20);
classNumber.setBounds(30, 180, 50, 15);
classNumbertext.setBounds(110, 180, 100, 20);
adress.setBounds(280, 180, 50, 15);
adresstext.setBounds(360, 180, 100, 20);
BaoCun.setBounds(80, 240, 80, 25);
BaoCun.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
BaoCunsaveAction(e);
} catch (Exception e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}

});
quit.setBounds(330, 240, 80, 25);
quit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dispose();
}
});
this.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
dispose();
}
});
add(id); add(name); add(sex); add(age); add(classNumber); add(idtext);
add(nametext); add(sextext); add(agetext); add(classNumbertext); add(BaoCun); add(quit);
add(adress); add(adresstext);
setLocationRelativeTo(null);
this.setVisible(true);
}
private void BaoCunsaveAction(ActionEvent e) throws Exception{
PreparedStatement sta2;
String id=null;
String name=null;
String sex=null;
String age=null;
String classNumber=null;
String adress=null;
id=idtext.getText();
name=nametext.getText().toString();
sex=sextext.getSelectedItem().toString();
age=agetext.getText().toString();
classNumber=classNumbertext.getText().toString();
adress=adresstext.getText().toString();
idtext.setText(id);
if(idtext.getText().toString().equals("")) {
JOptionPane.showMessageDialog(null,"抱歉学号不能为空");
return;
}
if(StudentExit(id)) {
JOptionPane.showMessageDialog(null,"学生已存在");
return;
}
id=idtext.getText();
String sql2="insert into information(id,name,sex,age,classNumber,adress)"+"values(?,?,?,?,?,?)";
sta2=(PreparedStatement)MySQL.prepareStatement(sql2);
sta2.setString(1,idtext.getText());
sta2.setString(2,name);
sta2.setString(3,sex);
sta2.setString(4,age);
sta2.setString(5,classNumber);
sta2.setString(6,adress);
int a=sta2.executeUpdate();
if(a==1) {
JOptionPane.showMessageDialog(null,"学生信息保存成功");
clear();
}
else {
JOptionPane.showMessageDialog(null,"学生信息保存失败");
}
}
private boolean StudentExit(String id) throws Exception {
PreparedStatement sta;
String sql="select * from information where id=?";
sta=MySQL.prepareStatement(sql);
sta.setString(1,idtext.getText());
ResultSet rs=sta.executeQuery();
if(rs.next()) {
return true;
}
else {
return false;
}
}
private void clear() {
idtext.setText(""); adresstext.setText("");
nametext.setText(""); agetext.setText("");
classNumbertext.setText("");
}
}
运行后如果添加新学生有java.lang.NullPointerException异常

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