哪位Java大佬能告诉我错在哪里？

 
package chazhao;
import com.baidubce.http.ApiExplorerClient;
import com.baidubce.http.AppSigner;
import com.baidubce.http.HttpMethodName;
import com.baidubce.model.ApiExplorerRequest;
import com.baidubce.model.ApiExplorerResponse;
import java.io.*;
import java.net.*;
public class chazhao {
    public static void main(String[] args) throws IOException  {
        FileWriter fileWriter = new FileWriter("手机号码.txt");
        String httpUrl = "http://gsd.api.bdymkt.com/sms";
        String httpArg = "";
        for (int i = 0; i < 9999; i++) {
            if (i >= 1000) {
                httpArg = "phone=135" + String.valueOf(i) + "0015";
            } else if (i >= 100) {
                httpArg = "phone=1350" + String.valueOf(i) + "0015";
            } else if (i >= 10) {
                httpArg = "phone=13500" + String.valueOf(i) + "0015";
            } else {
                httpArg = "phone=135000" + String.valueOf(i) + "0015";
            }
            String jsonResult = request(httpUrl, httpArg);
            if (jsonResult.contains("上海")) {
                fileWriter.write(httpArg + "\n\t");
            }
        }
        fileWriter.flush();
        fileWriter.close();
    }
 
    /**
     * @param urlAll  :请求接口
     * @param httpArg :参数
     * @return 返回结果
     */
    public static String request(String httpUrl, String httpArg) {
        BufferedReader reader = null;
        String result = null;
        StringBuffer sb = new StringBuffer();
        httpUrl = httpUrl + "?" + httpArg;
        try {
            URL url = new URL(httpUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();//打开url连接
            connection.setConnectTimeout(15000);//设置连接超时时间
            connection.setReadTimeout(15000);//设置读取超时时间
            connection.setRequestMethod("POST");//设置请求参数，即具体的http方法
            // 填入apikey到HTTP header
            connection.setRequestProperty("apikey", " *************");
            connection.setDoOutput(true);//设置是否向httpUrlConnection输出；对于post请求，参数要放在http正问内，因此需要设置为true(默认情况下是false)
            connection.setDoInput(true);//设置是否从httpUrlConnection读入，默认情况下是true
            connection.connect();//调用connect连接远程资源
            InputStream is = connection.getInputStream();//利用getInputStream()访问资源数据
            BufferedReader reader1 = new BufferedReader(new InputStreamReader(is, "UTF-8"));
            String strRead = null;
            while ((strRead = reader1.readLine()) != null) {
                sb.append(strRead);
                sb.append("\r\n");
            }
            reader.close();
            result = sb.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
 
}