写一个java的增删改查

以下是一个简单的 Java 增删改查示例：

import java.sql.*;

public class CRUDExample {
    private Connection conn;

    public CRUDExample() {
        try {
            // 连接数据库
            String url = "jdbc:mysql://localhost:3306/mydatabase";
            String user = "root";
            String password = "password";
            conn = DriverManager.getConnection(url, user, password);
            System.out.println("连接成功");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void insert(String name, int age) {
        try {
            // 插入数据
            String sql = "INSERT INTO person (name, age) VALUES (?, ?)";
            PreparedStatement stmt = conn.prepareStatement(sql);
            stmt.setString(1, name);
            stmt.setInt(2, age);
            stmt.executeUpdate();
            System.out.println("插入成功");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void update(int id, String name, int age) {
        try {
            // 更新数据
            String sql = "UPDATE person SET name = ?, age = ? WHERE id = ?";
            PreparedStatement stmt = conn.prepareStatement(sql);
            stmt.setString(1, name);
            stmt.setInt(2, age);
            stmt.setInt(3, id);
            stmt.executeUpdate();
            System.out.println("更新成功");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void delete(int id) {
        try {
            // 删除数据
            String sql = "DELETE FROM person WHERE id = ?";
            PreparedStatement stmt = conn.prepareStatement(sql);
            stmt.setInt(1, id);
            stmt.executeUpdate();
            System.out.println("删除成功");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void select() {
        try {
            // 查询数据
            String sql = "SELECT * FROM person";
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery(sql);
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                System.out.println("id: " + id + ", name: " + name + ", age: " + age);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        CRUDExample example = new CRUDExample();
        example.insert("Tom", 20);
        example.insert("Jerry", 25);
        example.update(1, "Tim", 22);
        example.delete(2);
        example.select();
    }
}

上述代码中，CRUDExample 类实现了对 person 表的增删改查操作。其中，insert、update 和 delete 方法通过执行 SQL 语句实现对数据库的修改，select 方法通过执行查询语句获取结果集并打印出来。在 main 方法中，我们创建了一个 CRUDExample 对象，然后调用其方法进行操作。