code: public void addSample(Sample stat) {
          samples.add(stat);
          if (samples.size() == 1) {
              start = stat.start;
              end = stat.end;
          }
          this.ioBytes += stat.ioBytes;
          this.jobMsgCnt += stat.jobMsgCnt;
          this.msgCnt += stat.msgCnt;
          this.msgBytes += stat.msgBytes;
          this.start = Math.min(this.start, stat.start);
          this.end = Math.max(this.end, stat.end);
      }
docs: Adds a sample to the group.
  
  @param stat the sample to add