code: @Override
      public Integer getCharge() {
          Integer charge = 0;
          Iterator<IMolecularFormula> componentIterator = components.iterator();
          while (componentIterator.hasNext()) {
              charge += componentIterator.next().getCharge();
          }
          return charge;
      }
docs: Returns the partial charge of this Adduct. If the charge
  has not been set the return value is Double.NaN.
  
  @return the charge of this Adduct
  
  @see    #setCharge