21:08:05 RandomGetRecord. java↵ import java. sql.*;↵ import java. util.*;↵ public class RandomGetRecord {↵ public static void main(String args[]){↵ int wantRecordAmount=10;随机抽取的记录数目↵ Random random=new Random();↵ try{ 【代码1】//加载JDBC-ODBC桥接器↵ }< catch(ClassNotFoundException e){↵ System. out. print(e);↵ }. Connection con;↵ Statement sql;↵ ResultSe t rs;↵ 21:09:00 try{ String uri="jdbc:odbc:dataSource";↵ String id="";↵ String password=””;↵ con=DriverManager. getConnection(uri, id, password);↵ sql= con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,↵ ResultSet.CONCUR_READ_ONLY);↵ rs=【代码2】//sql调用. executeQuery方法查询goods表中的全部记录↵ rs. last(); /将rs的游标移到rs的最后一行↵ _ int count=rs. getRow(); Vector<Integer>vector=new Vector<Integer>0;↵ for(int i=1;i<=count;i++) { ↵ vector. add(new Integer(i));↵ } ↵ int itemAmount=Math . min(wantRecordAmount, count);↵ System. out. println("随机抽取"+itemAmount+"条记录.");↵ double sum =0,n=itemAmount;↵ while(itemAmount>0){↵ int randomIndex =random. nextInt(vector. size());↵ int index=(vector. elementAt(randomIndex)). intValue();↵ 【代码3】//将rs的游标游标移到index↵ String number =rs. getString(1);↵ String name=rs. getString(2);↵ java. util. Date date=rs. getDate(3);↵ double price=rs. getDouble(4);↵ sum=sum+price;↵ itemAmount--; vector. removeElementAt(randomIndex);↵ } con. close();↵ double aver=sum/n;↵ System. out. println("均价:"+aver+"元");↵ } catch(SQLException e){↵ 21:10:55 System.out.println(“”+e)；

import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; import java.util.ArrayList; import java.util.List; //import Account.java; public class JDBCResultSet<Stu> { public void testResultSet() throws Exception { Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql:///test01?useSSL=false"; String username = "root"; String password = "03928"; Connection conn = DriverManager.getConnection(url, username, password); String sql = "select * from account"; Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery(sql); List<Stu> list = new ArrayList<>(); while (rs.next()){ Stu student = new Stu(); } } }出现Type parameter 'Stu' cannot be instantiated directly这个错误如何处理

public class Student { private int id; private String name; // ... public Student(int id, String name) { this.id = id; this.name = name; } // ... } 2. 在您的方法中，使用ResultSet对象来...

package DiLiuZhang; import java.sql.Date; import java.util.Date; public class Circle { public static void main(String[] args) { java.sql.Date date=new java.sql.Date(); java.util.Date date1=new java.util.Date(); } }

原因是在该代码中同时导入了 java.sql.Date 和 java.util.Date，两者名称相同，会发生冲突。需要对其中一个进行重命名，或者使用全限定名来避免冲突。以下是修改后的代码： java package DiLiuZhang; ...

package day0608.utils; import com.alibaba.druid.pool.DruidDataSource; import com.alibaba.druid.pool.DruidDataSourceFactory; import javax.sql.DataSource; import java.io.IOException; import java.io.InputStream; import java.util.Properties; /** * 连接池工具类

import java.util.Properties; 2. 创建连接池工具类 java public class ConnectionPoolUtil { private static DataSource dataSource; static { try { // 读取配置文件 InputStream inputStream = ...

优化这段代码：package com.ethan.dao; import java.awt.List; import java.sql.Connection; import java.sql.ResultSet; import java.util.ArrayList; import com.ethan.model.; import com.ethan.util.DBUtil; import com.mysql.jdbc.PreparedStatement; public class StudentDao { private static Connection conn = DBUtil.getConn(); private static PreparedStatement pstmt = null; private static ResultSet rs = null; public static ArrayList<Student> findAllStuden() throws Exception { String sql = "select from student"; pstmt = (PreparedStatement) conn.prepareStatement(sql); ResultSet rs = pstmt.executeQuery(); ArrayList<Student> list = new ArrayList<Student>(); while (rs.next()) { Student student = new Student(); student.setUserId(Integer.parseInt(rs.getString("userId"))); student.setUserName(rs.getString("userName")); student.setSex(rs.getString("sex")); student.setBirthYear(rs.getString("birthYear")); student.setGrade(rs.getString("grade")); student.setCollegeName(rs.getString("collegeName")); list.add(student); } return list; } }

import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; public class StudentDao { public static List<Student> findAllStudent() throws ...

帮我优化下面这段代码：package com.ethan.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import com.ethan.model.Student; import com.ethan.util.DBUtil; public class StudentDao { private static Connection conn = DBUtil.getConn(); private static PreparedStatement pstmt = null; private static ResultSet rs = null; public static List<Student> findAllStudent() throws Exception { String sql = "select * from student"; pstmt = conn.prepareStatement(sql); ResultSet rs = pstmt.executeQuery(); List<Student> list = new ArrayList<Student>(); while (rs.next()) { Student student = new Student(); student.setUserId(rs.getInt("userId")); student.setUserName(rs.getString("userName")); student.setSex(rs.getString("sex")); student.setBirthYear(rs.getString("birthYear")); student.setGrade(rs.getString("grade")); student.setCollegeName(rs.getString("collegeName")); list.add(student); } return list; } }

import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import com.ethan.model.Student; import com.ethan.util.DBUtil; public class StudentDao...

package data3; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLDataException; import java.sql.SQLException; import java.text.ParseException; import java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.Scanner; import data3.test.classselect; public class main { private static List<tele> telelist=new ArrayList<tele>(); public static void main(String[] args) throws ClassNotFoundException, SQLException { Scanner scanner = new Scanner(System.in); int choice; while (true) { displayMenu(); choice = scanner.nextInt(); scanner.nextLine(); // 清除输入缓冲区中的换行符 switch (choice) { case 1: showUserList(); break; case 2: update(); break; case 3: Insert(); break; case 4: delete(); break; case 0: System.out.println("感谢使用！"); return; default: System.out.println("无效的选项，请重新输入。"); } } } private static void displayMenu() { System.out.println("------------------手机营销充值中心----------------"); System.out.print("1. 查看手机用户列表"); System.out.print(" 2. 充值"); System.out.print(" 3. 新用户注册"); System.out.print(" 4. 老用户注销"); System.out.println(" 0. 退出"); System.out.print("请选择操作："); } private static List<tele> showUserList() throws SQLException { Connection conn=null; PreparedStatement pst =null; ResultSet rs =null; try { conn = classselect.getConnection(); String sql = "select * from phone"; pst = conn.prepareStatement(sql); rs = pst.executeQuery(); List<tele；；这是一串代码，请帮我完善

String sql = "update phone set balance=balance+? where phone=?"; pst = conn.prepareStatement(sql); pst.setInt(1, amount); pst.setString(2, phone); int rows = pst.executeUpdate(); if (rows > 0) { ...

package studentsSystem; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.Properties; import javax.sql.DataSource; import com.alibaba.druid.pool.DruidDataSourceFactory; public class system { public static void main(String[] args) throws Exception{ // TODO Auto-generated method stub； Properties prop=new Properties(); prop.load(new FileInputStream("shixun/src/druid.properties")); DataSource dataSource=DruidDataSourceFactory.createDataSource(prop); Connection conn=dataSource.getConnection(); String sql="update student set 姓名=王五 where 学号=01"; PreparedStatement pstm=conn.prepareStatement(sql); ResultSet rs=pstm.executeQuery(); pstm.close(); conn.close(); } }

这段代码的作用是使用阿里巴巴的 Druid 数据库连接池框架连接到数据库，并执行一个 SQL 更新语句，将学号为 01 的学生的姓名修改为“王五”。具体实现步骤如下： 1. 读取数据库连接池的配置信息，这些信息保存在 ...

package com.xxx.dao; import java.util.HashMap; import java.util.List; import java.util.Map; import org.mybatis.spring.SqlSessionTemplate; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Repository; import com.xxx.bean.Order; @Repository public class OrderDao { private final static String NAMESPACE = "com.xxx.dao.OrderDao."; @Autowired private SqlSessionTemplate sqlSessionTemplate; public List<Order> getOrderByUid(Long u_id){ Map<String, Object> paramMap = new HashMap<>(); paramMap.put("u_id",u_id); return sqlSessionTemplate.selectList(NAMESPACE + "getOrderByUid", paramMap); } }

这个常量可能用于构建SQL语句的命名空间或者作为Mapper文件中SQL语句的前缀。该类还定义了一个名为getOrderByUid的方法，它接收一个Long类型的参数u_id，并返回一个List对象。方法内部使用了一个Map对象paramMap，...

package main.java.reader.service; import java.util.List; import main.java.librarian.dataClass.Book; import main.java.reader.bean.BForm; import main.java.reader.bean.Rd; import main.java.dbSQL.BFormdao; public class BFormService { Book book=new Book(); BFormdao dao=new BFormdao(); public List<Book> select_by_id(Book bf) { List<Book> aList=dao.select_by_id(bf); return aList; } public List<Book> select_by_isbn(Book bf) { List<Book> aList=dao.select_by_isbn(bf); return aList; } public List<BForm> selectByBookNameAndReaderId(String BookName,String ReaderId){ List<BForm> bList=dao.selectByBookNameAndReaderId(BookName,ReaderId); return bList; } public List<BForm> selectByISBNAndReaderId(String ISBN,String ReaderId){ List<BForm> bList=dao.selectByISBNAndReaderId(ISBN,ReaderId); return bList; } }

这是一个 Java 类，名为 BFormService，它提供了一些方法用于查询数据库中的数据。其中，select_by_id() 方法和 select_by_isbn() 方法分别通过书籍的编号和 ISBN 号来查询书籍信息，并返回一个 Book 类型的列表。...

补全代码根据班级查找学生信息(支持模糊查找)，并输出学生信息。最终运行结果如下: 学生姓名:汪罗睿所在班级:软工1503 生日: 1995-11-02 性别:男址:北京市利星行广场微软大厦206体验中心联系电话: 13939688375 ** ★- ★★★★★ 学生姓名:王玉强所在班级:软工1503 生日: 1995-09-07 性别:男址:吉林省长春市东南湖大路1281号联系电话: 16070958343 轩 **** * 学生姓名:王浩所在班级:软工1502 生日: 1996-02-09 性别:男址:福建省福州市湖东路中大厦，兴业银行联系电话: 15851868080 学生姓名:包敦喜所在班级:软工1503 生日: 1995-05-15 性别:男住址:北京市西城区阜成i ]外大街29号，联系电话: 17215808700 ** package jdbc.score.dao.impl; import java.util.List; import org.springframework.jdbc.core.JdbcTemplate; import jdbc.score.dao.StudentDao; import jdbc.score.entities.Student; import jdbc.score.mapper.StudentMapper; public class StudentMapper implements RowMapper<Student> { //自定义映射规则 public Student mapRow(ResultSet arg0, int arg1) throws SQLException { // TODO Auto-generated method stub ...........（代码1） }

import java.util.List; import org.springframework.jdbc.core.JdbcTemplate; import jdbc.score.dao.StudentDao; import jdbc.score.entities.Student; import jdbc.score.mapper.StudentMapper; public class ...

package com.xdj.trustedsign.entity; import com.baomidou.mybatisplus.annotation.IdType; import com.baomidou.mybatisplus.annotation.TableField; import com.baomidou.mybatisplus.annotation.TableId; import com.baomidou.mybatisplus.annotation.TableName; import lombok.Data; import org.xdj.base.BaseEntity; import java.io.Serializable; import java.util.Date; /** * @Author: liuzhenwei * @Date: 2023/04/11 10:20 * @Description: */ @TableName("signature_b_temp") @Data public class SignatureBTemp extends BaseEntity<SignatureBTemp> { @TableId(type = IdType.ASSIGN_UUID) private String id; @TableField("signer_id") private String signerId; @TableField("account_id") private String accountId; @TableField("signature_image") private String signatureImage; @TableField("firsttime") private Date firsttime; @TableField("signature_url") private String signatureUrl; @TableField("dqzt") private String dqzt; @Override public Serializable pkVal() { return this.id; } }根据这个实体类写一个sql表语句

根据这个实体类，可以写出对应的建表语句如下： CREATE TABLE signature_b_temp ( id VARCHAR(32) NOT NULL, signer_id VARCHAR(32), account_id VARCHAR(32), signature_image VARCHAR(255), ...

帮我优化这段代码，谢谢package com.neutech.utils; import java.sql.*; import java.util.ArrayList; import java.util.List; public class Jdbcutil { private static final String DRIVERNAME = "org.apache.hive.jdbc.HiveDriver"; private static final String URL = "jdbc:hive2://192.168.44.199:10000/test"; private static final String USERNAME = "root"; private static final String PASSWORD = "200812"; public static Connection getConnection() throws ClassNotFoundException { Class.forName(DRIVERNAME); Connection connection = null; try { connection = DriverManager.getConnection(URL,USERNAME,PASSWORD); } catch (SQLException throwables) { throwables.printStackTrace(); } return connection; } public static <T> List<T> execuetQuery(String sql, RowMap<T> rowMap, Object... objs) throws ClassNotFoundException, SQLException { // 建立连接 Connection connection = getConnection(); PreparedStatement preparedStatement = connection.prepareStatement(sql); // 注入额外条件 if(objs != null){ for(int i = 0;i <= objs.length;i++){ preparedStatement.setObject(i + 1,objs[i]); } } ResultSet resultSet = preparedStatement.executeQuery(); ArrayList<T> list = new ArrayList<>(); while(resultSet.next()){ T t = rowMap.RowMapping(resultSet); list.add(t); } return list; } public static void close(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet) throws SQLException { connection.close(); preparedStatement.close(); resultSet.close(); } }

import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import java.util.Properties; public class JdbcUtil { ...

import java.rmi. import java.rml.server.UnicastRemoteObject import java.sql. import java.util. public class ConvertionServerlmpl extends UnicastRemoteObject lmplements ConvertionServer( publlc ConvertionServerlmpl( throws RemoteException! super0); public int convert(int amount) throws RemoteException( return amount"40:) public static vold main(String args)( System.setSecurityManager(new RMISecurityManager()); y ConvertionServerlmpl instance = new ConvertionServerlmpl0 Naming.rebind("ConvertionServer" instance) System.outprintln("Server Registered"): ) catch(Exception e) System.err.printn(e);}}} 写出远程接口的正确代码!

根据给出的远程接口实现类 ConvertionServerlmpl，我们可以推断出远程接口的方法签名为 public int convert(int amount) throws RemoteException。因此，以下是正确的远程接口代码： java import java.rmi....

package connectmysql; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; import java.util.Scanner; import java.sql.SQLException; import java.sql.Statement; public class text { private final static String url ="jdbc:mysql://localhost:3306/mytextsql?severTimezone=GMT"; private final static String username="root"; private final static String password="yxh9497"; public static void main(String args[]) { try { Class.forName("com.mysql.cj.jdbc.Driver"); }catch(Exception e) { e.printStackTrace(); } try { Connection connect=DriverManager.getConnection(url,username,password); Statement stmt=connect.createStatement(); Scanner a=new Scanner(System.in); System.out.print("删除的是:"+'\n'); String a4=a.next(); String sql="delete from user where name="+a4; int i=stmt.executeUpdate(sql); if(i > 0){ System.out.println("删除成功"); } }catch(Exception e) { e.printStackTrace(); } } }

import java.util.Scanner; import java.sql.SQLException; public class text { private final static String url ="jdbc:mysql://localhost:3306/mytextsql?severTimezone=GMT"; private final static String ...

package com.util; import java.sql.Connection; import java.util.Random; import java.sql.*; import com.util.SQLConn; public class RandomStringGenerator { public RandomStringGenerator() throws SQLException{ // 构造函数中调用可能会抛出SQLException异常的方法 // 添加异常处理语句 try{ final String UPDATE_SQL = "INSERT INTO strings (value) VALUES (?)"; try { Connection conn = SQLConn.openDB(); Class.forName("com.sqlserver.jdbc.Driver"); // 生成随机字符串 Random rand = new Random(); StringBuilder sb = new StringBuilder(); for (int i = 0; i < 5; i++) { char c = (char) (rand.nextInt(26) + 'a'); sb.append(c); } String str = sb.toString(); // 保存到数据库 PreparedStatement pstmte = conn.prepareStatement(UPDATE_SQL); { pstmte.setInt(1, 1); pstmte.executeUpdate(); } System.out.println("随机字符串已保存到数据库中：" + str); pstmte.close(); conn.close(); } catch (ClassNotFoundException e) { e.printStackTrace(); } }catch(SQLException e){ // exception handling here throw e; } }优化代码

import java.sql.PreparedStatement; import java.sql.SQLException; import java.util.Random; public class RandomStringGenerator { private static final String INSERT_SQL = "INSERT INTO strings (value) ...

package com.rain.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import com.rain.bean.AdminBean; import com.rain.bean.ProblemBean; import com.rain.util.DBUtil; public class ProblemDao {

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package com.rain.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import com.rain.bean.AdminBean; import com.rain.bean.ProblemBean; import com.rain.util.DBUtil; public class ProblemDao {

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