private WordField[] asNonEmptyArray(List<WordField> words) {
        if (words != null && !words.isEmpty()) {
            WordField[] wordsArray = new WordField[words.size()];
            words.toArray(wordsArray);
            return wordsArray;
        } else {
            return null;
        }
    }
Put the words in URL into bag of words

@param urlStr String
@param wordsFields Vector list of word
ache/src/main/java/achecrawler/link/classifier/builder/LinkNeighborhoodWrapper.java