code: private static void processBiGram() {
          //移除二元模型出现频率为1的情况
          Iterator<String> iter = BIGRAM.keySet().iterator();
          while(iter.hasNext()){
              String key = iter.next();
              if(BIGRAM.get(key) < 2){
                  iter.remove();
              }
          }
          try(BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("src/main/resources/bigram.txt"),"utf-8"))){
              for(Entry<String, Integer> item : BIGRAM.entrySet()){
                  writer.write(item.getKey()+" "+item.getValue()+"\n");
              }
          }catch(Exception e){
              LOGGER.info("保存bigram模型失败：", e);
          }
      }
docs: 分析处理并存储二元模型
  移除二元模型出现频率为1的情况
  排序后保存到bigram.txt文件