code: @Override public Double evaluate(List<S> solutionList) {
      if (solutionList == null) {
        throw new JMetalException("The pareto front approximation is null") ;
      }
  
      return invertedGenerationalDistancePlus(new ArrayFront(solutionList), referenceParetoFront);
    }
docs: Evaluate() method
  @param solutionList
  @return