code: public RunTime addDetail(String description){
  		RunTime child = new RunTime(description);
  		detail.put(description, child);
  		return child;
  	}
docs: Create a detail record and add it as a child.<br>
  创建一条详细记录并加为下级。
  
  @param description	Any text that describes the detailed RunTime.
  @return	The detailed RunTime created.