code: public void skipGram(int i, List<VocabWord> sentence, int b, double alpha) {
  
          final VocabWord word = sentence.get(i);
          if (word != null && !sentence.isEmpty()) {
              int end = window * 2 + 1 - b;
              for (int a = b; a < end; a++) {
                  if (a != window) {
                      int c = i - window + a;
                      if (c >= 0 && c < sentence.size()) {
                          VocabWord lastWord = sentence.get(c);
                          iterateSample(word, lastWord, alpha);
                      }
                  }
              }
          }
      }
docs: Train via skip gram
  @param i
  @param sentence