code: public void setChapterNumber(int number) {
      	numbers.set(numbers.size() - 1, Integer.valueOf(number));
      	Object s;
      	for (Iterator i = iterator(); i.hasNext(); ) {
      		s = i.next();
      		if (s instanceof Section) {
      			((Section)s).setChapterNumber(number);
      		}
      	}
      }
docs: Changes the Chapter number.