code: public void add(@NotNull String gram) {
          if (name == null) throw new IllegalStateException();
          int len = gram.length();
          if (len < 1 || len > NGram.N_GRAM) {
              throw new IllegalArgumentException("ngram length must be 1-3 but was "+len+": >>>"+gram+"<<<!");
          }
          nWords[len - 1]++;
          if (freq.containsKey(gram)) {
              freq.put(gram, freq.get(gram) + 1);
          } else {
              freq.put(gram, 1);
          }
      }
docs: Add n-gram to profile
  @param gram