code: public void addFreq(int index, int freq) {
          switch (index) {
              case 11:
                  this.end += freq;
                  allFreq += freq;
                  break;
              case 12:
                  this.end += freq;
                  this.begin += freq;
                  allFreq += freq;
                  break;
              case 44:
                  this.split += freq;
                  allFreq += freq;
                  break;
          }
      }
docs: 设置
  
  @param index
  @param freq