code: public static String getStandardHeaderValue(final HttpURLConnection conn, final String headerName) {
          final String headerValue = conn.getRequestProperty(headerName);
  
          // Coalesce null value
          return headerValue == null ? Constants.EMPTY_STRING : headerValue;
      }
docs: Returns the standard header value from the specified connection request, or an empty string if no header value
  has been specified for the request.
  
  @param conn
  An <code>HttpURLConnection</code> object that represents the request.
  @param headerName
  A <code>String</code> that represents the name of the header being requested.
  
  @return A <code>String</code> that represents the header value, or <code>null</code> if there is no corresponding
  header value for <code>headerName</code>.