public long getNthPercentileFinishTime(int percentile)
  {
    if(finishTimes == null || finishTimes.size() == 0 ) {
      return -1;
    }
    return Statistics.percentile(finishTimes, percentile);
  }
Returns the nth percentile finish job
@param percentile The percentile of finish job to return
@return The nth percentile finish job
app/com/linkedin/drelephant/tez/TezTaskLevelAggregatedMetrics.java