使用JDBC对数据进行分组

import java.sql.*;

public class JDBCTest {
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            // 建立数据库连接
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");

            // 创建Statement对象
            statement = connection.createStatement();

            // 编写SQL语句
            String sql = "SELECT category, COUNT(*) FROM products GROUP BY category";

            // 执行SQL语句
            resultSet = statement.executeQuery(sql);

            // 处理查询结果
            while (resultSet.next()) {
                String category = resultSet.getString(1);
                int count = resultSet.getInt(2);
                System.out.println("Category: " + category + ", Count: " + count);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (statement != null) {
                    statement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}