code: public static String getFileContent(InputStream is) throws IOException {
          BufferedReader buff = new BufferedReader(new InputStreamReader(is,
                  "UTF-8"));
          String content = getContent(buff);
          buff.close();
          return content;
      }
docs: 按照UTF-8编码得到输入流内容
  
  @param is 输入流
  @return 文件内容
  @throws IOException io exception