code: public void addIsotope(IIsotope isotope, int countMin, int countMax) {
          
          if (isotope == null) 
              throw new IllegalArgumentException("Isotope must not be null");
          
          boolean flag = false;
          for (Iterator<IIsotope> it = isotopes().iterator(); it.hasNext();) {
              IIsotope thisIsotope = it.next();
              if (isTheSame(thisIsotope, isotope)) {
                  isotopesMax.put(thisIsotope, countMax);
                  isotopesMin.put(thisIsotope, countMin);
                  flag = true;
                  break;
              }
          }
          if (!flag) {
              isotopesMax.put(isotope, countMax);
              isotopesMin.put(isotope, countMin);
          }
      }
docs: Adds an Isotope to this MolecularFormulaExpand in a number of
  maximum and minimum occurrences allowed.
  
  @param  isotope  The isotope to be added to this MolecularFormulaExpand
  @param  countMax The maximal number of occurrences to add
  @param  countMin The minimal number of occurrences to add