code: public Date getFinishDate()
     {
        Date result = (Date) getCachedValue(ProjectField.FINISH_DATE);
        if (result == null)
        {
           result = getParentFile().getFinishDate();
        }
        return (result);
     }
docs: Retrieves the project finish date. If an explicit finish date has not been
  set, this method calculates the finish date by looking for
  the latest task finish date.
  
  @return Finish Date