code: public static String getSummary(String document, int max_length, String sentence_separator)
      {
          List<String> sentenceList = splitSentence(document, sentence_separator);
  
          int sentence_count = sentenceList.size();
          int document_length = document.length();
          int sentence_length_avg = document_length / sentence_count;
          int size = max_length / sentence_length_avg + 1;
          List<List<String>> docs = convertSentenceListToDocument(sentenceList);
          TextRankSentence textRank = new TextRankSentence(docs);
          int[] topSentence = textRank.getTopSentence(size);
          List<String> resultList = new LinkedList<String>();
          for (int i : topSentence)
          {
              resultList.add(sentenceList.get(i));
          }
  
          resultList = permutation(resultList, sentenceList);
          resultList = pick_sentences(resultList, max_length);
          return TextUtility.join("。", resultList);
      }
docs: 一句话调用接口
  
  @param document   目标文档
  @param max_length 需要摘要的长度
  @param sentence_separator 句子分隔符，正则格式， 如：[。？?！!；;]
  @return 摘要文本