code: protected void writeFieldInstContent(OutputStream result) throws IOException 
      {
          result.write(HYPERLINK);
          result.write(DELIMITER);
          this.document.filterSpecialChar(result, url, true, true);
      }
docs: Write the field instructions for this RtfAnchor. Sets the field
  type to HYPERLINK and then writes the url.
  
  @param result The <code>OutputStream</code> to write to.
  @throws IOException on i/o errors.