java将数据存入mysql后，我用另外一个java class查看不了，请问怎么解决？
我在“请输入存款金额”的那个java class中，输入了存款1000的数额，弹窗显示存入成功
但是在后面这个java class点开余额查询，还是显示您的余额为0，怎么让我在存款后，在余额查询那里显示出来
数据表bank中的amount的列是显示有存入存款的金额，但是我跑这个java class，点击余额查询没有显示出应该有的余额，怎么解决？
第一个存入存款的java class
package bank.management.system;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
public class Deposit extends JFrame implements ActionListener{
JTextField t1,t2;
JButton b1,b2,b3;
JLabel l1,l2,l3;
String pin;
Deposit(String pin){
this.pin = pin;
ImageIcon i1 = new ImageIcon(ClassLoader.getSystemResource("icons/atm.jpg"));
Image i2 = i1.getImage().getScaledInstance(840, 1000, Image.SCALE_DEFAULT);
ImageIcon i3 = new ImageIcon(i2);
JLabel l3 = new JLabel(i3);
l3.setBounds(0, 0, 800, 900);
add(l3);
l1 = new JLabel("请输入存款金额");
l1.setForeground(Color.WHITE);
l1.setFont(new Font("System", Font.BOLD, 16));
t1 = new JTextField();
t1.setFont(new Font("Raleway", Font.BOLD, 22));
b1 = new JButton("存款");
b2 = new JButton("返回");
setLayout(null);
l1.setBounds(130,280,400,18);
l3.add(l1);
t1.setBounds(130,330,320,25);
l3.add(t1);
b1.setBounds(300,470,150,35);
l3.add(b1);
b2.setBounds(300,510,150,35);
l3.add(b2);
b1.addActionListener(this);
b2.addActionListener(this);
setSize(800, 660);
setUndecorated(true);
setVisible(true);
setLocation(250,10);
}
public void actionPerformed(ActionEvent ae){
try{
String amount = t1.getText();
Date date = new Date();
if(ae.getSource()==b1){
if(t1.getText().equals("")){
JOptionPane.showMessageDialog(null, "请输入存款金额");
}else{
Conn c1 = new Conn();
c1.s.executeUpdate("insert into bank values('"+pin+"', '"+date+"', 'Deposit', '"+amount+"')");
JOptionPane.showMessageDialog(null, "存款成功，存入金额： ￥. "+amount);
setVisible(false);
new Transactions(pin).setVisible(true);
}
}else if(ae.getSource()==b2){
setVisible(false);
new Transactions(pin).setVisible(true);
}
}catch(Exception e){
e.printStackTrace();
}
}
public static void main(String[] args){
new Deposit("").setVisible(true);
}
}
第二个查询存款的java class
package bank.management.system;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;
public class MiniStatement extends JFrame implements ActionListener{
JButton b1, b2;
JLabel l1;
MiniStatement(String pin){
super("交易明细查询");
getContentPane().setBackground(Color.WHITE);
setSize(400,600);
setLocation(20,20);
l1 = new JLabel();
add(l1);
JLabel l2 = new JLabel("中国邮政银行");
l2.setBounds(150, 20, 100, 20);
add(l2);
JLabel l3 = new JLabel();
l3.setBounds(20, 80, 300, 20);
add(l3);
JLabel l4 = new JLabel();
l4.setBounds(110, 430, 300, 20);
add(l4);
try{
Conn c = new Conn();
ResultSet rs = c.s.executeQuery("select * from login where pin = '"+pin+"'");
while(rs.next()){
l3.setText("Card Number: " + rs.getString("cardnum").substring(0, 4) + "XXXXXXXX" + rs.getString("cardno").substring(12));
}
}catch(Exception e){}
try{
double balance = 0;
Conn c1 = new Conn();
ResultSet rs = c1.s.executeQuery("SELECT * FROM bank where pin = '"+pin+"'");
while(rs.next()){
l1.setText(l1.getText() + "<html>"+rs.getString("date")+ " " + rs.getString("type") + " " + rs.getString("amount") + "<br><br><html>");
if(rs.getString("type").equals("Deposit")){
balance += Double.parseDouble(rs.getString("amount"));
}else{
balance -= Double.parseDouble(rs.getString("amount"));
}
}
l4.setText("余额查询 "+balance);
}catch(Exception e){
e.printStackTrace();
}
setLayout(null);
b1 = new JButton("退出");
add(b1);
b1.addActionListener(this);
l1.setBounds(20, 140, 400, 200);
b1.setBounds(20, 500, 100, 25);
}
public void actionPerformed(ActionEvent ae){
this.setVisible(false);
}
public static void main(String[] args){
new MiniStatement("").setVisible(true);
}
}
数据库看下有没有相关的数据
你先确定下是不是真的存进数据库了？mysql打开表里看下。
第二，我都没看到你数据库有加载驱动，确定成功存入了？
- 以下回答由chatgpt基于相关博客总结生成:
由于缺乏具体代码和数据结构的信息，无法得知具体原因。但是在一般情况下，当存款成功后余额查询却显示为0的原因可能是没有正确更新余额信息。解决方法可能如下：
- 确认amount列是正确保存了存款金额，可以在mysql控制台中输入以下命令查看：
select amount from bank where id=[账户id];- 确认查询余额的java class中使用的是正确的sql语句，应该是类似如下的查询语句：
select balance from bank where id=[账户id];- 在存款时，应该通过sql更新余额信息，而不是重新计算余额。示例如下：
```java //假设已经连接到数据库，并且传入了账户id和存款金额 //首先查询当前余额 String sql1 = "select balance from bank where id = ?"; PreparedStatement ps1 = conn.prepareStatement(sql1); ps1.setInt(1, accountId); ResultSet rs1 = ps1.executeQuery(); rs1.next(); int currentBalance = rs1.getInt(1);
//更新余额 String sql2 = "update bank set balance = ? where id = ?"; PreparedStatement ps2 = conn.prepareStatement(sql2); ps2.setInt(1, currentBalance + depositAmount); ps2.setInt(2, accountId); ps2.executeUpdate(); ```
- 如果以上步骤都正确，但仍然无法正确查询余额，则可能是使用了缓存，导致查询不到最新的余额信息。可以在查询余额之前，调用以下语句强制刷新缓存：
java conn.createStatement().execute("SELECT @@cache_block_size"); //执行任意sql语句即可清空缓存以下是两个Java class的示例代码，其中Bank类保存了账户信息，包括账户id、余额和存款方法。另外一个类TestBank用于测试，包括存款和查询余额两个方法：
Bank类代码：
public class Bank { private int id; private int balance; public Bank(int id, int balance) { this.id = id; this.balance = balance; } public int getBalance() { return balance; } public void deposit(int amount) { balance += amount; } public int getId() { return id; } }TestBank类代码：
import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; public class TestBank { private static final String DB_DRIVER = "com.mysql.jdbc.Driver"; private static final String DB_URL = "jdbc:mysql://localhost:3306/test"; private static final String DB_USERNAME = "root"; private static final String DB_PASSWORD = "root"; public static void main(String[] args) { //连接数据库 Connection conn = null; try { Class.forName(DB_DRIVER); conn = DriverManager.getConnection(DB_URL, DB_USERNAME, DB_PASSWORD); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } //测试存款 Bank bank = new Bank(1, 100); bank.deposit(50); updateAccount(conn, bank); //测试查询余额 int balance = getBalance(conn, 1); System.out.println("余额为：" + balance); //关闭数据库连接 try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } private static int getBalance(Connection conn, int accountId) { String sql = "select balance from bank where id = ?"; PreparedStatement ps = null; ResultSet rs = null; int balance = 0; try { ps = conn.prepareStatement(sql); ps.setInt(1, accountId); rs = ps.executeQuery(); if (rs.next()) { balance = rs.getInt("balance"); } } catch (SQLException e) { e.printStackTrace(); } finally { //关闭结果集、预编译语句和连接 try { rs.close(); ps.close(); } catch (SQLException e) { e.printStackTrace(); } } return balance; } private static void updateAccount(Connection conn, Bank bank) { String sql = "update bank set balance = ? where id = ?"; PreparedStatement ps = null; try { ps = conn.prepareStatement(sql); ps.setInt(1, bank.getBalance()); ps.setInt(2, bank.getId()); ps.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } finally { //关闭预编译语句 try { ps.close(); } catch (SQLException e) { e.printStackTrace(); } } } }