有时在0的字符0处抛出输入的结尾

I am trying to develop an application that using JSON parser between PHP and my mobile application, and I found that most of the time the application is running normally, but few times, less that 10% will throw the error of end of input at character 0. Can anyone have a briefly explain on what have I encountered?

Here is my code for getting the data from PHP:

public class getDataClass {

 public void onCreate(Bundle savedInstanceState) {
        StrictMode.ThreadPolicy policy = new      StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);      }
    public static String executeQuery() {
        String result = "";

        try {
            HttpParams httpParameters = new BasicHttpParams();
            HttpConnectionParams.setConnectionTimeout(httpParameters, 6000);
            HttpConnectionParams.setSoTimeout(httpParameters, 6000);
            //check IF IP timeout
            HttpClient httpClient = new DefaultHttpClient(httpParameters);

            HttpPost httpPost = new HttpPost("somephp.php");
            //ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
           // params.add(new BasicNameValuePair("query_string", query_string));
        //    httpPost.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
            HttpResponse httpResponse = httpClient.execute(httpPost);
            //view_account.setText(httpResponse.getStatusLine().toString());
            HttpEntity httpEntity = httpResponse.getEntity();
            InputStream inputStream = httpEntity.getContent();

            BufferedReader bufReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"), 8);
            StringBuilder builder = new StringBuilder();
            String line = null;
            while((line = bufReader.readLine()) != null) {
                builder.append(line + "
");
            }
            inputStream.close();
            result = builder.toString();
        } catch(Exception e) {
            // Log.e("log_tag", e.toString());
        }

        return result;
    }
}

And here is the method that i use in my main activity:

private String DLdata(){

    String result = getDataClass.executeQuery();          
    if(result.startsWith("[")){             
    }else{
    result = result.substring(1);
    }
    return result;

}