package text6; import java.sql.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class domo extends JFrame implements ActionListener{ Connection con; Statement cmd; ResultSet rs; String url="jdbc:mysql://127.0.0.1:3306/support"; String driver="com.mysql.jdbc.Driver"; JPanel jp1=new JPanel(); JPanel jp2=new JPanel(); JLabel lbl_no=new JLabel("学号"); JLabel lbl_name=new JLabel("姓名"); JLabel lbl_birth=new JLabel("生日"); JLabel lbl_sex=new JLabel("性别"); JLabel lbl_study=new JLabel("学情"); JLabel lbl_live=new JLabel("宿舍"); JTextField txt_no=new JTextField(20); JTextField txt_name=new JTextField(20); JTextField txt_birth=new JTextField(20); JTextField txt_sex=new JTextField(20); JTextField txt_study=new JTextField(20); JTextField txt_live=new JTextField(20); JButton btn_add=new JButton("新增"); JButton btn_delete=new JButton("删除"); JButton btn_update=new JButton("更新"); public domo(){ jp1.add(lbl_no); jp1.add(txt_no); jp1.add(lbl_name); jp1.add(txt_name); jp1.add(lbl_birth); jp1.add(txt_birth); jp1.add(lbl_sex); jp1.add(txt_sex); jp1.add(lbl_study); jp1.add(txt_study); jp1.add(lbl_live); jp1.add(txt_live); add(jp1,BorderLayout.CENTER); jp2.add(btn_add); jp2.add(btn_delete); jp2.add(btn_update); add(jp2,BorderLayout.SOUTH); btn_add.addActionListener(this); btn_delete.addActionListener(this); btn_update.addActionListener(this); setBounds(250,250,250,250); setVisible(true); setDefaultCloseOperation(DISPOSE_ON_CLOSE); } public void actionPerformed(ActionEvent e) { if(btn_add.isSelected()) { try { Class.forName(driver); con=DriverManager.getConnection(url,"root",""); cmd=con.createStatement(); String sql="select * from student where sno='" + txt_no.getText() + "'";//查看是否存在已有的uno rs=cmd.executeQuery(sql); if(rs.next()) if(rs.getString(1).equals(txt_no.getText())==false) JOptionPane.showMessageDialog(null, "成功","成功",JOptionPane.PLAIN_MESSAGE); con.close(); }catch(Exception e1) { System.out.print(e1); } } } public static void main(String args[]) { JFrame.setDefaultLookAndFeelDecorated(true); new domo(); } }改错

java课程设计图书馆管理系统.doc

import java.awt.event.ActionListener; import javax.swing.AbstractAction; import javax.swing.Icon; import javax.swing.ImageIcon; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing...

Java课程设计超市库存管理系统附源代码可以直接运行.doc

import java.awt.event.*; import javax.swing.*; import java.sql.*; public class LoginFrame extends JFrame { // ... } 四、软件测试 ---------------- 系统测试包括功能测试、性能测试和安全测试等方面...

package DMS.SYSTEM; import DMS.GetConnection; import DMS.Users; import javax.swing.; import javax.swing.table.DefaultTableModel; import javax.swing.table.TableRowSorter; import java.awt.; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.sql.*; /**学生缺寝 * @author LQ * @create */ public class CooBuilding extends JPanel implements ActionListener { Connection connection = new GetConnection().GetConnection(); int type; Users user; JTable table = new JTable(); //JButton button = new JButton(""); String[] col = {"楼名", "层数", "管理人","容纳人数"}; DefaultTableModel mm = new DefaultTableModel(col, 0); // 定义一个表的模板 JLabel Bname,Bfloor,Bmager,Bcap,SP; JTextField BnameText,BfloorText,BmagerText,BcapText; JButton seek, add, delete, edit; JPanel student; public CooBuilding(int type, Users user) { this.user = user; this.type = type; setLayout(new FlowLayout());//整个采用流动式布局很好的适应了表格带来的影响 table.setModel(mm); table.setRowSorter(new TableRowSorter<>(mm)); JScrollPane js = new JScrollPane(table); add(js); search(); }

这段代码是一个 Java 类，名为 CooBuilding，继承自 JPanel 类，并且实现了 ActionListener 接口。这个类主要是用来显示一个包含建筑物信息的表格，并且可以对这个表格进行增删改查的操作。其中，变量 type 表示用户...

package package06; import java.awt.; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.sql.; import javax.swing.*; public class Java6 extends JFrame { JLabel wenzi; JTextField shuru; JButton chaxun; JTextArea fanhui; public Java6(){ super("中英查询软件"); // 窗口添加pNorth 在北面区域 add(getNorthPanel(),BorderLayout.NORTH); } private JPanel getNorthPanel() { JPanel panel = new JPanel(); wenzi = new JLabel("请输入要查询的单词："); shuru=new JTextField(8); chaxun=new JButton("查询"); fanhui =new JTextArea(6,25); panel.add(wenzi,new FlowLayout()); panel.add(shuru,new FlowLayout()); panel.add(chaxun,new FlowLayout()); panel.add(fanhui,new FlowLayout()); return panel; } public static void main(String[] args) throws Exception{ Java6 zy=new Java6(); zy.setBounds(100, 100, 340, 170); zy.setVisible(true); zy.setDefaultCloseOperation(zy.EXIT_ON_CLOSE); Class.forName("com.mysql.cj.jdbc.Driver"); //加载MySQL的驱动类 String ur1="jdbc:mysql://localhost:3306/java实训"; String user="root"; String password="root"; try { Connection Con =DriverManager.getConnection(ur1,user,password); System.out.println("eeeeee"); } catch (Exception e) { // TODO: handle exception System.out.println("ww"); } } }这些代码连接不了数据库，是哪里错误了吗？

import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.sql.*; import javax.swing.*; public class Java6 extends JFrame { JLabel wenzi; JTextField shuru; JButton ...

优化这段代码package com.daiinfo.catering.pane; import com.daiinfo.catering.util.JDBConnection; import javax.swing.; import javax.swing.border.Border; import java.awt.; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.EventListener; public class DishManagePane2 extends JFrame { private JTable table; private JButton addButton,updateButton,deleteButton; public DishManagePane2(){ setTitle("菜品管理"); setSize(800,600); String [] columnNames = {"菜品名","价格","菜品类别"}; Object[][] data = {{"糖醋排骨",29.0,"西餐"},{"宫保鸡丁",28.0,"中餐"}}; JTable table = new JTable(data,columnNames); addButton = new JButton("增加"); updateButton = new JButton("修改"); deleteButton = new JButton("删除"); addButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { } }); JPanel panel = new JPanel(new BorderLayout()); panel.add(new JScrollPane(table),BorderLayout.CENTER); JPanel buttonPanel = new JPanel(new FlowLayout()); buttonPanel.add(addButton); buttonPanel.add(updateButton); buttonPanel.add(deleteButton); panel.add(buttonPanel,BorderLayout.SOUTH); add(panel); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } public static void main(String[] args) { new JDBConnection(); new DishManagePane2(); } }

import java.awt.event.ActionListener; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Vector; public class ...

package 软件本科9班小罗; import java.awt.; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.beans.Statement; import java.sql.; import javax.swing.*; public class Java06 extends JFrame implements ActionListener{ JButton Button; JLabel s1; JTextField text; JTextArea ta; Connection conn; java.sql.Statement stat1; java.sql.Statement stat2; ResultSet rs1,rs2; public Java06() { super("中英文查询"); Button=new JButton("查询"); Button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { chazhao(); } }); s1=new JLabel("输入要查询的单词:"); text =new JTextField("word",20); ta = new JTextArea("工作",7,36); JPanel panel=new JPanel(); panel.add(s1); panel.add(text); panel.add(Button); JPanel panel2=new JPanel(); panel2.add(ta); Container con=getContentPane(); con.add(panel,BorderLayout.NORTH); con.add(panel2); setSize(400,200); } public void chazhao() { String i; try { Class.forName("com.mysql.jdbc.Driver");//加载连接驱动; conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/sys?serverTimezone=UTC", "root", "123456"); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block System.out.println("加载驱动失败"); } catch (SQLException e) { System.out.println("获取连接失败"); } String sql1="select 中文 from book where 英文="+"\""+text+"\""; String sql2="select 英文 from book where 中文="+"\""+text+"\""; try { stat1=conn.createStatement(); rs1=stat1.executeQuery(sql1); stat2=conn.createStatement(); rs2=stat2.executeQuery(sql2); while(rs1.next()) { System.out.println(rs1.getString("中文")); } while (rs2.next()) { System.out.println(rs2.getString("英文")); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static void main(String[] args) { new Java06().setVisible(true); } @Override public void actionPerformed(ActionEvent e) { // TODO Auto-generated method stub if(e.getSource()==Button) { String text=ta.getText(); ta.setText(text);; } } }这个代码中哪里有错呀，运行不了，还连接不成数据库

3. SQL查询语句错误。你的查询语句可能有问题。你需要检查语句是否正确，并且确定你的数据库中是否有名为“book”的表。 4. 代码中的其他潜在错误。在代码中有其他的潜在错误，例如未处理异常或变量命名错误。你...

此代码应如何修改避免空指针异常package frame; import dao.ProductDAO; import dao.ProductDAOImpl; import model.Product; import javax.swing.; import java.awt.; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.sql.SQLException; public class UpdateProductDialog extends JDialog { private boolean isOK = false; private Product product; private JTextField nameField; private JTextField priceField; private JTextArea descriptionArea; public UpdateProductDialog(Frame owner, int productId) { super(owner, "更新商品", true); setPreferredSize(new Dimension(400, 300)); setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); ProductDAO productDAO = new ProductDAOImpl() { @Override public Product getProductById(int id) { return null; } }; product = productDAO.getProductById(productId); JLabel nameLabel = new JLabel("名称"); JLabel priceLabel = new JLabel("价格"); JLabel descriptionLabel = new JLabel("描述"); nameField = new JTextField(product.getName()); priceField = new JTextField(Double.toString(product.getPrice())); descriptionArea = new JTextArea(product.getDescription(), 5, 20); JButton okButton = new JButton("确定"); okButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { String name = nameField.getText(); double price = Double.parseDouble(priceField.getText()); String description = descriptionArea.getText(); product.setName(name); product.setPrice(price); product.setDescription(description); isOK = true; dispose(); } }); JButton cancelButton = new JButton("取消"); cancelButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { dispose(); } }); JPanel panel = new JPanel(new GridLayout(4, 2)); panel.add(nameLabel); panel.add(nameField); panel.add(priceLabel); panel.add(priceField); panel.add(descriptionLabel); panel.add(new JScrollPane(descriptionArea)); panel.add(okButton); panel.add(cancelButton); setContentPane(panel); pack(); setLocationRelativeTo(owner); } public boolean isOK() { return isOK; } public Product getProduct() { return product; } }

在这段代码中，空指针异常可能会出现在以下行： product = productDAO.getProductById(productId); 如果productDAO返回的是null，那么product也将是null，在接下来的代码执行中，如果你尝试使用...

package text6; import java.sql.; import java.awt.; import java.awt.event.; import javax.swing.; public class domo extends JFrame implements ActionListener{ JPanel jp1=new JPanel(); JPanel jp2=new JPanel(); JLabel lbl_no=new JLabel("学号"); JLabel lbl_name=new JLabel("姓名"); JLabel lbl_birth=new JLabel("生日"); JLabel lbl_sex=new JLabel("性别"); JLabel lbl_study=new JLabel("学情"); JLabel lbl_live=new JLabel("宿舍"); JTextField txt_no=new JTextField(20); JTextField txt_name=new JTextField(20); JTextField txt_birth=new JTextField(20); JTextField txt_sex=new JTextField(20); JTextField txt_study=new JTextField(20); JTextField txt_live=new JTextField(20); JButton btn_add=new JButton("新增"); JButton btn_delete=new JButton("删除"); JButton btn_update=new JButton("更新"); public domo(){ jp1.add(lbl_no); jp1.add(txt_no); jp1.add(lbl_name); jp1.add(txt_name); jp1.add(lbl_birth); jp1.add(txt_birth); jp1.add(lbl_sex); jp1.add(txt_sex); jp1.add(lbl_study); jp1.add(txt_birth); jp1.add(lbl_live); jp1.add(txt_live); add(jp1,BorderLayout.CENTER); jp2.add(btn_add); jp2.add(btn_delete); jp2.add(btn_update); add(jp2,BorderLayout.SOUTH); setBounds(250,250,250,250); setVisible(true); } @Override public void actionPerformed(ActionEvent e) { // TODO 自动生成的方法存根 } public static void main(String args[]) { JFrame.setDefaultLookAndFeelDecorated(true); new domo(); } }改错

package text6; import java.sql.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class domo extends JFrame implements ActionListener{ JPanel jp1=new JPanel(); ...

修改这段代码实现选择表格一行信息删除package frame; import javax.swing.; import java.awt.; import java.awt.event.ActionEvent; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.SQLException; //添加页面 public class EditDialog extends BaseDialog{ DataChangelisenter dataChangelisenter; public void setDataChangelisenter(DataChangelisenter dataChangelisenter) { this.dataChangelisenter = dataChangelisenter; } @Override public void init() { setLayout(new FlowLayout()); //布局 setTitle("修改图书信息"); JPanel jp0=new JPanel(); JLabel l0 = new JLabel("id"); JTextField t0 = new JTextField(); t0.setPreferredSize(new Dimension(300,30)); jp0.add(l0); jp0.add(t0); JPanel jp1=new JPanel(); JLabel l1 = new JLabel("书名"); JTextField t1 = new JTextField(); t1.setPreferredSize(new Dimension(300,30)); jp1.add(l1); jp1.add(t1); JPanel jp2=new JPanel(); JLabel l2 = new JLabel("作者"); JTextField t2 = new JTextField(); t2.setPreferredSize(new Dimension(300,30)); jp2.add(l2); jp2.add(t2); JPanel jp3=new JPanel(); JLabel l3 = new JLabel("分类"); JTextField t3 = new JTextField(); t3.setPreferredSize(new Dimension(300,30)); jp3.add(l3); jp3.add(t3); JPanel jp4=new JPanel(); JLabel l4 = new JLabel("出版社"); JTextField t4 = new JTextField(); t4.setPreferredSize(new Dimension(300,30)); jp4.add(l4); jp4.add(t4); JPanel jp5=new JPanel(); JLabel l5 = new JLabel("数量"); JTextField t5 = new JTextField(); t5.setPreferredSize(new Dimension(300,30)); jp5.add(l5); jp5.add(t5); add(jp0); add(jp1); add(jp2); add(jp3); add(jp4); add(jp5); JButton b1 = new JButton("保存"); b1.setPreferredSize(new Dimension(150,30)); b1.addActionListener(new AbstractAction() { @Override public void actionPerformed(ActionEvent e) { String id = t0.getText(); String sname = t1.getText(); String author = t2.getText(); String classify = t3.getText(); String press = t4.getText(); String quantity = t5.getText(); Connection con = DBUtil.getConnect(); String sql = "UPDATE tushu SET sname=?,author=?,classify=?,press=?,quantity=? WHERE id=?"; try { PreparedStatement ps = con.prepareStatement(sql); ps.setString(1,sname); ps.setString(2,author); ps.setString(3,classify); ps.setString(4,press); ps.setString(5,quantity); ps.setString(6,id); int result = ps.executeUpdate(); if (result>0){ JOptionPane.showMessageDialog(EditDialog.this,"修改成功"); // new StudentFrame(); dataChangelisenter.dataChange(); dispose(); }else { JOptionPane.showMessageDialog(EditDialog.this,"修改失败"); } } catch (SQLException throwables) { throwables.printStackTrace(); } } }); add(b1); } }

import java.awt.event.ActionEvent; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.SQLException; public class EditDialog extends BaseDialog{ DataChangelisenter ...

create database student; use student; create table users( uname varchar(10) primary key, upwd varchar(10) ); insert into users values('admin','1234'); insert into users values('zhou','zhou');package homework7_二_2_20221548; import javax.swing.; import java.awt.; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.sql.; public class Demo { public static void main(String args[]){ MyWindow win=new MyWindow(); } } class MyWindow extends JFrame{ JLabel lbl_name=new JLabel("username"); JLabel lbl_password=new JLabel("password"); JTextField txt_name=new JTextField(15); JTextField txt_password=new JTextField(15); JButton btn1=new JButton("confirm"); JButton btn2=new JButton("cancel"); MyWindow(){ JPanel jp1=new JPanel(); jp1.setLayout(new FlowLayout()); jp1.add(lbl_name); jp1.add(txt_name); jp1.add(lbl_password); jp1.add(txt_password); add(jp1,BorderLayout.CENTER); JPanel jp2=new JPanel(); jp2.setLayout(new FlowLayout()); jp2.add(btn1); jp2.add(btn2); btn1.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { String txt1=txt_name.getText(); String txt2=txt_password.getText(); String[] username=new String[2]; String[] password=new String[2]; new DemoQuery(username,password); if(txt1.equals(username[0])&&txt2.equals(password[0])) { JOptionPane.showMessageDialog(null,"欢迎您，"+username[0]+"登录"); } else if(txt1.equals(username[1])&&txt2.equals(password[1])){ JOptionPane.showMessageDialog(null,"欢迎您，"+username[1]+"登录"); } else { JOptionPane.showMessageDialog(null,"用户名和密码错误"); txt_name.setText(""); txt_password.setText(""); } } }); add(jp2,BorderLayout.SOUTH); setSize(300,150); setVisible(true); setTitle("the login window"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } } class DemoQuery { public DemoQuery(String[] username,String[] password){ String url = "jdbc:mysql://127.0.0.1:3306/student"; String user = "root", pwd = ""; Connection con; Statement sql; ResultSet rs; try { Class.forName("com.mysql.jdbc.Driver"); } catch (ClassNotFoundException e) { System.out.println("test" + e); } try { con = DriverManager.getConnection(url, user, pwd); sql = con.createStatement(); String sqlStatement; sqlStatement = "SELECT From users"; rs = sql.executeQuery(sqlStatement); while (rs.next()) { int i = 0; username[i] = rs.getString("uname"); password[i] = rs.getString("upwd"); System.out.println(username[i]+" "+password[i]); i++; } con.close(); } catch (SQLException e) { System.out.println("数据库操作失败" + e); } } }为什么用户名输入admin，密码输入1234显示登录失败？

rs = sql.executeQuery(sqlStatement); int i = 0; while (rs.next()) { username[i] = rs.getString("uname"); password[i] = rs.getString("upwd"); System.out.println(username[i]+" "+password[i]); i++...

在util包中写DbUtil类：定义方法，实现数据库的连接和关闭。 5．在model包中创建用户实体类User 。包含id、userName、userPwd成员变量；构造方法； getXxx()、setXxx()方法 6．在view包中添加登录窗体类LoginFrame（包含mian方法），MainFrame窗体类。 7．在dao包中：创建UserDao类，定义添加数据的方法，public int userAdd(Connection con,User user)（在main方法中调用该方法实现向数据库中插入数据）；创建LoginDao类，通过用户名和密码查询用户的方法，public static User login(Connection con,User user) 。 8. 为LoginFrame登录窗体的“登录”按钮和“注册”按钮添加监听器并处理单击事件。登录时，输入正确的用户名和密码，弹出MainFrame窗体；输入错误，弹出提示框。9.为Register注册窗体的“确定”和“取消”按钮添加监听器并处理单击事件。注册成功弹出消息提示框，两次密码不一致，弹出提示框。点击“取消”按钮，textField内容清空，可重新输入。给出java代码

import java.awt.event.ActionListener; import java.sql.Connection; import java.sql.SQLException; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing....

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