docs: private static void ngramOnCharacter(String data, int[] gramSizes, Collection<String> list) {
      	data = data.replaceAll("\\s+", "");
      	for (int j = 0; j < gramSizes.length; j++) {
              int len = gramSizes[j];
              if (len <= 0 || len > data.length())
                  continue;
              for (int i = 0; i < data.length() - len; i++) {
                  list.add(data.substring(i, i + len));
              }
          }
      }