code: protected int addWordToVocab(String word)
      {
          vocab[vocabSize] = new VocabWord(word);
          vocabSize++;
  
          // Reallocate memory if needed
          if (vocabSize + 2 >= vocabMaxSize)
          {
              vocabMaxSize += 1000;
              VocabWord[] temp = new VocabWord[vocabMaxSize];
              System.arraycopy(vocab, 0, temp, 0, vocabSize);
              vocab = temp;
          }
          vocabIndexMap.put(word, vocabSize - 1);
          return vocabSize - 1;
      }
docs: Adds a word to the vocabulary
  
  @param word
  @return