code: public static String guessEncodingByMozilla(byte[] bytes) {
          String DEFAULT_ENCODING = "UTF-8";
          UniversalDetector detector = new UniversalDetector(null);
          detector.handleData(bytes, 0, bytes.length);
          detector.dataEnd();
          String encoding = detector.getDetectedCharset();
          detector.reset();
          if (encoding == null) {
              encoding = DEFAULT_ENCODING;
          }
          return encoding;
      }
docs: 根据字节数组，猜测可能的字符集，如果检测失败，返回utf-8
  
  @param bytes 待检测的字节数组
  @return 可能的字符集，如果检测失败，返回utf-8