java水果超市登陆代码 java水果系统

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求大神指点，这是我用java写的超市管理系统，登录就出现这

这都是小问题。从LoginServletjava水果超市登陆代码的doPost方法查找下去!我猜啊，可能是java水果超市登陆代码你没处理null这种情况才出现java水果超市登陆代码的错误java水果超市登陆代码！比如一个对象为null就不应该拿来再用

了，用之前呢先判断下java水果超市登陆代码！具体错因你可以自己查下是什么，可能没连接到数据库或找不到对应的数据等等返回了个null值，而此时你没做判断又用了它而造成的！重启下服务器看看。

相关问答

Q1: 亲有java语言写的超市管理系统课程设计和源代码吗，能给我吗

package untitled5;

import java.io.*;

import java.net.*;

import java.sql.*;

import java.lang.*;

import javax.sql.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import com.borland.jbcl.layout.*;

public class delbook extends JFrame {

JPanel contentPane;

XYLayout xYLayout1 = new XYLayout();

JLabel jLabel1 = new JLabel();

JLabel jLabel2 = new JLabel();

JLabel jLabel3 = new JLabel();

JTextField jTextField1 = new JTextField();

JLabel jLabel4 = new JLabel();

JTextField jTextField2 = new JTextField();

JLabel jLabel5 = new JLabel();

JTextField jTextField3 = new JTextField();

JLabel jLabel6 = new JLabel();

JTextField jTextField4 = new JTextField();

JButton jButton1 = new JButton();

//Construct the frame

public delbook() {

enableEvents(AWTEvent.WINDOW_EVENT_MASK);

try {

jbInit();

}

catch(Exception e) {

e.printStackTrace();

}

//Component initialization

private void jbInit() throws Exception {

contentPane = (JPanel) this.getContentPane();

jLabel1.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel1.setForeground(Color.red);

jLabel1.setText("超市管理系统");

contentPane.setLayout(xYLayout1);

this.setSize(new Dimension(500,400));

this.setTitle("超市管理系统");

jLabel2.setFont(new java.awt.Font("SansSerif", 0, 30));

jLabel2.setText("业务单位信息");

jLabel3.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel3.setText("产品编号");

jTextField1.setText("");

jLabel4.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel4.setText("公司名称");

jTextField2.setText("");

jLabel5.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel5.setText("订单号码");

jTextField3.setText("");

jLabel6.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel6.setText("电话");

jTextField4.setText("");

jButton1.setFont(new java.awt.Font("SansSerif", 0, 25));

jButton1.setText("提交");

jButton1.addActionListener(new delbook_jButton1_actionAdapter(this));

contentPane.add(jLabel1, new XYConstraints(179, 1, 153, 32));

contentPane.add(jLabel2, new XYConstraints(162, 33, -1, -1));

contentPane.add(jLabel3, new XYConstraints(83, 89, -1, -1));

contentPane.add(jTextField1, new XYConstraints(189, 88, 141, 36));

contentPane.add(jTextField2, new XYConstraints(189, 149, 142, 36));

contentPane.add(jLabel4, new XYConstraints(84, 148, -1, -1));

contentPane.add(jTextField3, new XYConstraints(188, 206, 143, 33));

contentPane.add(jLabel5, new XYConstraints(84, 204, -1, -1));

contentPane.add(jLabel6, new XYConstraints(84, 253, -1, -1));

contentPane.add(jTextField4, new XYConstraints(189, 260, 143, 36));

contentPane.add(jButton1, new XYConstraints(197, 318, -1, -1));

}

//Overridden so we can exit when window is closed

protected void processWindowEvent(WindowEvent e) {

super.processWindowEvent(e);

if (e.getID() == WindowEvent.WINDOW_CLOSING) {

System.exit(0);

}

void update() {

try {

//定义显示java水果超市登陆代码的字符串

String str1;

String str2;

String str3;

String str4;

str1 = jTextField1.getText();

str2 = jTextField2.getText();

str3 = jTextField3.getText();

str4 = jTextField4.getText();

//装载jdbc驱动程序

String driverName = "oracle.jdbc.OracleDriver";

Driver driver = (Driver) Class.forName(driverName).newInstance();

//连接数据库

Connection con = DriverManager.getConnection(

"jdbc:oracle:thin:@thsspc0791:1521:liuyong", "hr", "tongfang");

PreparedStatement pstmt = con.prepareStatement(

" insert Customer1('goodID','Name','PID','tel')values(?,?,?,?)");

pstmt.setString(1, str1);

pstmt.setString(2, str2);

pstmt.setString(1, str3);

pstmt.setString(4, str4);

ResultSet res = pstmt.executeQuery();

pstmt.close();

con.close();

}catch (InstantiationException e) {

System.out.println(e.getMessage());

}catch (IllegalAccessException e) {

System.out.println(e.getMessage());

}catch (ClassNotFoundException e) {

System.out.println(e.getMessage());

}catch (SQLException edd) {

edd.printStackTrace() ;

System.out.println(edd.getMessage());

}

void jButton1_actionPerformed(ActionEvent e) {

update();

}

class delbook_jButton1_actionAdapter implements java.awt.event.ActionListener {

delbook adaptee;

delbook_jButton1_actionAdapter(delbook adaptee) {

this.adaptee = adaptee;

}

public void actionPerformed(ActionEvent e) {

adaptee.jButton1_actionPerformed(e);

}

package untitled5;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import com.borland.jbcl.layout.*;

/**

* pTitle: /p

* pDescription: /p

* pCompany: /p

* @author not attributable

* @version 1.0

public class retur extends JFrame {

JPanel contentPane;

XYLayout xYLayout1 = new XYLayout();

JLabel jLabel1 = new JLabel();

//Construct the frame

public retur() {

enableEvents(AWTEvent.WINDOW_EVENT_MASK);

try {

jbInit();

}

catch(Exception e) {

e.printStackTrace();

}

//Component initialization

private void jbInit() throws Exception {

contentPane = (JPanel) this.getContentPane();

jLabel1.setFont(new java.awt.Font("SansSerif", 0, 20));

jLabel1.setForeground(Color.red);

jLabel1.setText("超市管理系统");

contentPane.setLayout(xYLayout1);

this.setSize(new Dimension(400, 300));

this.setTitle("超市管理系统");

contentPane.add(jLabel1, new XYConstraints(139, 1, 126, 33));

}

//Overridden so we can exit when window is closed

protected void processWindowEvent(WindowEvent e) {

super.processWindowEvent(e);

if (e.getID() == WindowEvent.WINDOW_CLOSING) {

System.exit(0);

}

package untitled5;

import java.io.*;

import java.net.*;

import java.sql.*;

import java.lang.*;

import javax.sql.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import com.borland.jbcl.layout.*;

import com.borland.dbswing.*;

//货品信息登记

public class Frame2 extends JFrame {

JPanel contentPane;

JLabel jLabel1 = new JLabel();

XYLayout xYLayout1 = new XYLayout();

JLabel jLabel2 = new JLabel();

JLabel jLabel3 = new JLabel();

JTextField jTextField1 = new JTextField();

JLabel jLabel4 = new JLabel();

JTextField jTextField2 = new JTextField();

JPanel jPanel1 = new JPanel();

XYLayout xYLayout2 = new XYLayout();

JScrollPane jScrollPane1 = new JScrollPane();

JLabel jLabel5 = new JLabel();

JTextField jTextField3 = new JTextField();

//Construct the frame

public Frame2() {

enableEvents(AWTEvent.WINDOW_EVENT_MASK);

try {

jbInit();

}

catch(Exception e) {

e.printStackTrace();

}

//Component initialization

private void jbInit() throws Exception {

contentPane = (JPanel) this.getContentPane();

contentPane.setLayout(xYLayout1);

this.setSize(new Dimension(600, 500));

this.setTitle("超市管理系统");

this.addHierarchyBoundsListener(new Frame2_this_hierarchyBoundsAdapter(this));

jLabel1.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel1.setForeground(Color.red);

jLabel1.setText("超市管理系统");

contentPane.setForeground(Color.black);

jLabel2.setFont(new java.awt.Font("SansSerif", 0, 30));

jLabel2.setText("产品信息展示");

// statusBar.setFont(new java.awt.Font("SansSerif", 0, 20));

jLabel3.setFont(new java.awt.Font("SansSerif", 0, 20));

jLabel3.setText("产品名称");

jTextField1.setText("");

jLabel4.setEnabled(true);

jLabel4.setFont(new java.awt.Font("SansSerif", 0, 20));

jLabel4.setText("产品ID号");

jTextField2.setText("");

jTextField2.addActionListener(new Frame2_jTextField2_actionAdapter(this));

jPanel1.setLayout(xYLayout2);

jLabel5.setFont(new java.awt.Font("SansSerif", 0, 25));

jLabel5.setForeground(Color.red);

jLabel5.setText("该产品详细信息");

jTextField3.setText("");

contentPane.add(jLabel1, new XYConstraints(237, 0, 153, 40));

contentPane.add(jLabel2, new XYConstraints(200, 47, 231, 58));

contentPane.add(jLabel3, new XYConstraints(47, 102, 101, 42));

contentPane.add(jTextField1, new XYConstraints(128, 108, 112, 34));

contentPane.add(jTextField2, new XYConstraints(361, 107, 109, 36));

contentPane.add(jPanel1, new XYConstraints(75, 166, 453, 277));

jPanel1.add(jScrollPane1, new XYConstraints(14, 8, 433, 221));

jScrollPane1.getViewport().add(jTextField3, null);

jPanel1.add(jLabel5, new XYConstraints(112, 240, -1, -1));

contentPane.add(jLabel4, new XYConstraints(278, 111, -1, -1));

}

//Overridden so we can exit when window is closed

protected void processWindowEvent(WindowEvent e) {

super.processWindowEvent(e);

if (e.getID() == WindowEvent.WINDOW_CLOSING) {

System.exit(0);

}

void Select() {

try {

String str1, str2;

str1 = jTextField1.getText();

str2 = jTextField2.getText();

Q2: 有谁有用JAVA编写的小型超市管理系统的源代码啊数据库用mysql 急啊

作业吧？找个类似的图书馆一类的东西改一下数据库不就行了？

Q3: 数据库如何用java写超市购物程序？

要使用Java编写超市购物程序，您需要使用Java数据库编程技术来连接到您的数据库并执行相关的数据库操作。在Java中，您可以使用JDBC（Java数据库连接）API来连接到数据库并执行SQL语句。例如，您可以使用JDBC API来执行以下操作：

创建数据库连接

执行增删改查（CRUD）操作

提交或回滚事务

执行存储过程和函数

查询数据库元数据

此外，您还可以使用Java的面向对象编程技术来封装数据库操作，以便更方便地在您的程序中使用。例如，您可以创建一个类来表示超市商品，并定义一些方法来执行商品的增删改查操作。这样，您就可以在程序中通过调用这些方法来简单地完成对数据库的操作，而不需要编写复杂的SQL语句。

Q4: java程序编写，显示水果的订购详情，定义一个带有参数的构造方法，这些参数用于存放产品，数量和价格

public class ShuiGuo{

private String chanpin;

private int number;

private float price;

public ShuiGuo(String chanpin,int number,float price){

this.chanpin = chanpin;

this.number = number ;

this.price = price;

}

//省略get.set方法

}

最后的需求没看懂。是说自己输入水果之后，在来取3种不同的吗

Q5: java超市计价系统代码

package entity;

public class Market {

private int id;//id

private int num;//数量

private String goods;//商品

private double price;//价格

public Market(int id, int num, String goods, double price) {

super();

this.id = id;

this.num = num;

this.goods = goods;

this.price = price;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public int getNum() {

return num;

}

public void setNum(int num) {

this.num = num;

}

public String getGoods() {

return goods;

}

public void setGoods(String goods) {

this.goods = goods;

}

public double getPrice() {

return price;

}

public void setPrice(double price) {

this.price = price;

}

public double calc( ){

double sum=price*num;

System.out.println("您消费共计："+sum+"￥");

return sum;

}

package test;

import java.util.HashMap;

import java.util.Map;

import java.util.Scanner;

import entity.Market;

public class Test {

private static MapInteger,Market goods=new HashMapInteger, Market();

public static void main(String[] args) {

System.out.println("-------超市计价系统-------");

String goods1="可口可乐";

String goods2="爆米花";

String goods3="益达";

printTable("编号","商品","价格");

printTable("1",goods1,"3.0￥");

printTable("2",goods2,"5.0￥");

printTable("3",goods3,"10.0￥");

goods.put(1, new Market(1, 1, goods1, 3.0));

goods.put(2, new Market(2, 1, goods2, 5.0));

goods.put(3, new Market(3, 1, goods3, 10.0));

Scanner input = new Scanner(System.in);

System.out.println("请输入商品的编号:");

int num = input.nextInt();

System.out.println("请输入商品的数量");

int amount = input.nextInt();

Market market = goods.get(num);

market.setNum(amount);

market.calc();

}

private static void printTable(String row1,String row2,String row3 ) {

System.out.print(row1);

int times=12;

if (row2!="商品") {

times=5;

}

for (int i = 0; i times; i++) {

System.out.print(" ");

}

System.out.print(row2);

for (int i = 0; i 10; i++) {

System.out.print(" ");

}

System.out.print(row3);

System.out.println("\n");

}

//测试结果：

-------超市计价系统-------

编号商品价格

1 可口可乐 3.0￥

2 爆米花 5.0￥

3 益达 10.0￥

请输入商品的编号:

请输入商品的数量

您消费共计：50.0￥

java水果超市登陆代码的介绍就聊到这里吧，感谢你花时间阅读本站内容，更多关于java水果系统、java水果超市登陆代码的信息别忘了在本站进行查找喔。

正文

求大神指点，这是我用java写的超市管理系统，登录就出现这

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