code: public long getTotalRunTime() {
  		if (detail.size() > 0){
  			long runTime = 0;
  			for (RunTime child: detail.values()){
  				runTime += child.getTotalRunTime();
  			}
  			return runTime;
  		}else{
  			return statistics.getSum();
  		}
  	}
docs: Get run time which is the add-up of the run duration of all threads.<br>
  获得实际的运行时间，它是所有线程的执行时间之和。
  
  @return add-up of the run duration of all threads