code: public static boolean isExcelFile(String filename)
      {
          String lowerFilename = filename.toLowerCase();
          return lowerFilename.endsWith("."+CommonFiles.XLS_EXT)
             || lowerFilename.endsWith("."+CommonFiles.XLSX_EXT);
      }
docs: Returns <CODE>true</CODE> if the given filename is an XLS or XLSX file.
  @param filename The filename to be checked
  @return <CODE>true</CODE> if the given filename is an XLS or XLSX file