Stream to String 帮助类

private String StreamToString(InputStream inputStream, String charset) {    try {        InputStreamReader inputStreamReader = new InputStreamReader(inputStream, charset);        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);        StringBuilder stringBuilder = new StringBuilder();        String s=null;        while((s=bufferedReader.readLine())!=null){            stringBuilder.append(s);        }        bufferedReader.close();        return stringBuilder.toString();    } catch (Exception e) {        e.printStackTrace();    }    return null;}