code: private List<Word> segSentence(final String sentence){
          if(sentence.length() == 1){
              if(KEEP_WHITESPACE){
                  List<Word> result = new ArrayList<>(1);
                  result.add(new Word(KEEP_CASE ? sentence : sentence.toLowerCase()));
                  return result;
              }else{
                  if(!Character.isWhitespace(sentence.charAt(0))){
                      List<Word> result = new ArrayList<>(1);
                      result.add(new Word(KEEP_CASE ? sentence : sentence.toLowerCase()));
                      return result;
                  }
              }
          }
          if(sentence.length() > 1){
              List<Word> list = segImpl(sentence);
              if(list != null){
                  if(PERSON_NAME_RECOGNIZE){
                      list = PersonName.recognize(list);
                  }
                  return list;
              }else{
                  LOGGER.error("文本 "+sentence+" 没有获得分词结果");
              }
          }
          return Collections.emptyList();
      }
docs: 将句子切分为词
  @param sentence 句子
  @return 词集合