insert into tb_user (userName, userAge, userPwd ,userPwd2)values (#{userName}, #{userAge}, #{userPwd}

这是一条 SQL 语句的片段，用于向名为 tb_user 的数据库表中插入一条记录。其中，#{userName}、#{userAge}、#{userPwd} 和 #{userPwd2} 是占位符，表示需要动态传入的参数值。这些占位符对应的值可以通过 Mybatis 的动态 SQL 功能来实现动态拼接。具体来说，当执行这条 SQL 语句时，Mybatis 会根据传入的参数值动态地替换掉占位符，从而生成最终的 SQL 语句。例如，如果传入的参数值为 userName = "Tom"、userAge = 20、userPwd = "123" 和 userPwd2 = "123"，则最终生成的 SQL 语句为：

insert into tb_user (userName, userAge, userPwd ,userPwd2) values ('Tom', 20, '123', '123')

这条 SQL 语句的作用是向 tb_user 表中插入一条记录，记录的字段分别为 userName、userAge、userPwd 和 userPwd2，对应的值为传入的参数值。

相关问题

create table User0 ( UserAccount varchar2(10) not null, UserID varchar2(10) not null, UserAge int, UserName varchar2(40), UserPassword varchar2(10), UserBalance float, UserPhone varchar2(10), UserQQ varchar2(10), UserWechat varchar2(10), UserProfession varchar2(30), UserSex varchar2(10), UserAddress varchar2(40), UserGrade varchar2(20), constraint PK_UserAccount primary key (UserAccount), constraint CK_UserAge check (UserAge>=0 and UserAge <= 100), constraint CK_UserBalance check (UserBalance>=0), constraint CK_UserGrade check (UserGrade = '钻石' or UserGrade = '金卡' or UserGrade = '银卡' or UserGrade = '普通'), constraint CK_UserSex check (UserSex = '男' or UserSex = '女') );把这段代码转化成java

以下是将该SQL语句转化为Java代码的示例：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class CreateTable {
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        try {
            // 加载数据库驱动
            Class.forName("oracle.jdbc.driver.OracleDriver");

            // 获取数据库连接
            String url = "jdbc:oracle:thin:@localhost:1521:ORCL";
            String username = "yourUsername";
            String password = "yourPassword";
            connection = DriverManager.getConnection(url, username, password);

            // 创建表格
            statement = connection.createStatement();
            String sql = "create table User0 ("
                    + "UserAccount varchar2(10) not null, "
                    + "UserID varchar2(10) not null, "
                    + "UserAge int, "
                    + "UserName varchar2(40), "
                    + "UserPassword varchar2(10), "
                    + "UserBalance float, "
                    + "UserPhone varchar2(10), "
                    + "UserQQ varchar2(10), "
                    + "UserWechat varchar2(10), "
                    + "UserProfession varchar2(30), "
                    + "UserSex varchar2(10), "
                    + "UserAddress varchar2(40), "
                    + "UserGrade varchar2(20), "
                    + "constraint PK_UserAccount primary key (UserAccount), "
                    + "constraint CK_UserAge check (UserAge>=0 and UserAge <= 100), "
                    + "constraint CK_UserBalance check (UserBalance>=0), "
                    + "constraint CK_UserGrade check (UserGrade = '钻石' or UserGrade = '金卡' or UserGrade = '银卡' or UserGrade = '普通'), "
                    + "constraint CK_UserSex check (UserSex = '男' or UserSex = '女') )";
            statement.executeUpdate(sql);

            System.out.println("Table created successfully!");

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (statement != null) {
                    statement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

需要注意的是，这里使用的是 Oracle 数据库驱动，如果需要使用其他数据库，需要更改相应的驱动。同时，需要将 `yourUsername` 和 `yourPassword` 替换为相应的用户名和密码。

构造一个 List<Student> ， Student 有 name 和 age 两个属性。将 List<Student> 转换成 List<User>。 User里有 userName 和 userAge两个属性。

可以使用 Java 8 的 Stream API 和 Lambda 表达式来实现这个需求：

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<Student> studentList = new ArrayList<>();
        studentList.add(new Student("Alice", 20));
        studentList.add(new Student("Bob", 21));
        studentList.add(new Student("Charlie", 22));
        
        List<User> userList = studentList.stream()
            .map(student -> new User(student.getName(), student.getAge()))
            .collect(Collectors.toList());
        
        // 输出转换后的 User 列表
        for (User user : userList) {
            System.out.println(user.getUserName() + " " + user.getUserAge());
        }
    }
}

class Student {
    private String name;
    private int age;
    
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    public String getName() {
        return name;
    }
    
    public int getAge() {
        return age;
    }
}

class User {
    private String userName;
    private int userAge;
    
    public User(String userName, int userAge) {
        this.userName = userName;
        this.userAge = userAge;
    }
    
    public String getUserName() {
        return userName;
    }
    
    public int getUserAge() {
        return userAge;
    }
}

输出结果为：

Alice 20
Bob 21
Charlie 22

可以看到，List<Student> 成功转换为了 List<User>，并且转换后的 User 列表中包含了 Student 列表中的所有元素。