code: public Duration getFinishVariance()
     {
        Duration variance = (Duration) getCachedValue(AssignmentField.FINISH_VARIANCE);
        if (variance == null)
        {
           TimeUnit format = getParentFile().getProjectProperties().getDefaultDurationUnits();
           variance = DateHelper.getVariance(getTask(), getBaselineFinish(), getFinish(), format);
           set(AssignmentField.FINISH_VARIANCE, variance);
        }
        return (variance);
     }
docs: Calculate the finish variance.
  
  @return finish variance