docs: public double get2DHV(List<? extends Solution<?>> solutionSet) {
      double hv = 0.0;
      if (solutionSet.size() > 0) {
        hv = Math.abs((solutionSet.get(0).getObjective(0) - referencePoint.getValue(0)) *
            (solutionSet.get(0).getObjective(1) - referencePoint.getValue(1)));
  
        for (int i = 1; i < solutionSet.size(); i++) {
          double tmp ;
          tmp = Math.abs((solutionSet.get(i).getObjective(0) - referencePoint.getValue(0)) * (solutionSet.get(i).getObjective(1) - solutionSet.get(i - 1).getObjective(1)));
          hv += tmp;
        }
      }
      return hv;
    }