如何使用java更改postgres用户的密码？

import java.sql.*;

public class ChangePostgresPassword {
    public static void main(String[] args) {
        String url = "jdbc:postgresql://localhost:5432/mydatabase";
        String username = "postgres";
        String password = "oldpassword";
        String newPassword = "newpassword";

        try {
            // 连接到数据库
            Connection connection = DriverManager.getConnection(url, username, password);

            // 构建更新密码的SQL语句
            String sql = "ALTER USER postgres WITH PASSWORD '" + newPassword + "'";

            // 执行SQL语句
            Statement statement = connection.createStatement();
            statement.executeUpdate(sql);

            System.out.println("密码已成功更改！");

            // 关闭连接
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}