code: private void setMediaContentLength(String rangeHeader) {
      if (rangeHeader == null) {
        return;
      }
      if (mediaContentLength == 0) {
        mediaContentLength = Long.parseLong(rangeHeader.substring(rangeHeader.indexOf('/') + 1));
      }
    }
docs: Sets the media content length from the HTTP Content-Range header (E.g a header of
  "Content-Range: 0-55/1000" would cause 1000 to be set. <code>null</code> headers do not set
  anything.
  
  @param rangeHeader in the HTTP response