code: @Override
      public double validate(IMolecularFormula formula) throws CDKException {
          logger.info("Start validation of ", formula);
          double isValid = 1.0;
          Iterator<IElement> itElem = MolecularFormulaManipulator.elements(formula).iterator();
          while (itElem.hasNext()) {
              IElement element = itElem.next();
              int occur = MolecularFormulaManipulator.getElementCount(formula, element);
              if (occur > hashMap.get(element.getSymbol())) {
                  isValid = 0.0;
                  break;
              }
          }
  
          return isValid;
      }
docs: Validate the occurrence of this IMolecularFormula.
  
  @param formula   Parameter is the IMolecularFormula
  @return          An ArrayList containing 9 elements in the order described above