java的增删改查代码_Java增删改查代码

以下是Java实现增删改查的示例代码：

### 连接数据库

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

public class DBUtil {

    private static final String URL = "jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8";
    private static final String USER = "root";
    private static final String PASSWORD = "root";

    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
}

### 增加数据

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class AddData {

    public static void main(String[] args) {
        Connection conn = DBUtil.getConnection();
        String sql = "INSERT INTO user (username, password, age) VALUES (?, ?, ?)";
        PreparedStatement pstmt;
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, "Tom");
            pstmt.setString(2, "123456");
            pstmt.setInt(3, 20);
            int result = pstmt.executeUpdate();
            System.out.println("添加了" + result + "条数据！");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

### 删除数据

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DeleteData {

    public static void main(String[] args) {
        Connection conn = DBUtil.getConnection();
        String sql = "DELETE FROM user WHERE id=?";
        PreparedStatement pstmt;
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, 1);
            int result = pstmt.executeUpdate();
            System.out.println("删除了" + result + "条数据！");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

### 修改数据

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class UpdateData {

    public static void main(String[] args) {
        Connection conn = DBUtil.getConnection();
        String sql = "UPDATE user SET age=? WHERE id=?";
        PreparedStatement pstmt;
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, 21);
            pstmt.setInt(2, 2);
            int result = pstmt.executeUpdate();
            System.out.println("修改了" + result + "条数据！");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

### 查询数据

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class QueryData {

    public static void main(String[] args) {
        Connection conn = DBUtil.getConnection();
        String sql = "SELECT * FROM user";
        PreparedStatement pstmt;
        ResultSet rs;
        try {
            pstmt = conn.prepareStatement(sql);
            rs = pstmt.executeQuery();
            while (rs.next()) {
                System.out.println("id：" + rs.getInt("id") + "，username：" + rs.getString("username") + "，password：" + rs.getString("password") + "，age：" + rs.getInt("age"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}