code: private void grow() {
          char[][] newPages;
  
          if (lastFilled != pageSize) {
              throw new IllegalStateException();
          }
          lastNo++;
          if (lastNo >= pages.length) {
              newPages = new char[lastNo * 5 / 2][];
              System.arraycopy(pages, 0, newPages, 0, lastNo);
              pages = newPages;
          }
          if (pages[lastNo] == null) {
              pages[lastNo] = new char[pageSize];
          }
          lastFilled = 0;
      }
docs: Adds a page at the end