code: public LanguageProfileBuilder addGram(String ngram, int frequency) {
          Map<String, Integer> map = ngrams.get(ngram.length());
          if (map==null) {
              map = new HashMap<>();
              ngrams.put(ngram.length(), map);
          }
          Integer total = map.get(ngram);
          if (total==null) total = 0;
          total += frequency;
          map.put(ngram, total);
          return this;
      }
docs: If the builder already has this ngram, the given frequency is added to the current count.