更新MySQL数据库( java.sql.SQLException: No value specified for parameter 1) 异常 解决方法

package com.swift;

import java.io.File;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;

import com.google.gson.Gson;

public class UpdateUrl {

    public static void main(String[] args) {

        File file = new File("D:\\java_date", "questionJson.json");
        String jsonResult = GetData.getData(file);
        Gson gson = new Gson();
        Root root = gson.fromJson(jsonResult, Root.class);
        List<Result> result = root.getResult();
        updateUrl(result);
    }

    private static void updateUrl(List<Result> result) {

        Connection conn = DBUtil.getConn();
        PreparedStatement ps = null;
        try {
            
            ps = conn.prepareStatement("update sw_question set url = ? where id=?)");
            for (int i = 0; i < result.size(); i++) {
                String str=result.get(i).getUrl();
                int id=result.get(i).getId();
                if (str != null && str.length() > 0) {
                    ps.setString(1, str.substring(str.lastIndexOf("/")+1));//图片的URL地址截图成图片名称后更新数据库
                    ps.setInt(2, id);
                }
                ps.executeUpdate();
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            DBUtil.closeAll(conn, ps, null);
        }
    }
}