code: public Iterable<String[]> toArrays() {
      checkState(!isClosed, WORKBOOK_CLOSED);
      Iterable<String[]> arraysIterable = Iterables.transform(sheet, item -> {
        List<String> list = rowToList(item);
        return list.toArray(new String[list.size()]);
      });
      return hasHeader ? Iterables.skip(arraysIterable, 1) : arraysIterable;
    }
docs: Converts the spreadsheet to String Arrays by an Array Iterable.
  
  @return String array Iterable