code: @Override
      public boolean compare(Object object) {
          if (!(object instanceof Isotope)) {
              return false;
          }
          if (!super.compare(object)) {
              return false;
          }
          Isotope isotope = (Isotope) object;
          if (isotope.getMassNumber() != null && massNumber != null
                  && isotope.getMassNumber().intValue() != this.getMassNumber().intValue()) return false;
          if (isotope.getMassNumber() == null && massNumber != null) return false;
          if (isotope.getExactMass() != null && exactMass != null) {
              double diff = Math.abs(isotope.getExactMass().doubleValue() - this.getExactMass().doubleValue());
              if (diff > 0.0000001) return false;
          }
          if (isotope.getExactMass() == null && exactMass != null) return false;
          if (isotope.getNaturalAbundance() != null && naturalAbundance != null) {
              double diff = Math.abs(isotope.getNaturalAbundance().doubleValue()
                      - this.getNaturalAbundance().doubleValue());
              if (diff > 0.0000001) return false;
          }
          if (isotope.getNaturalAbundance() == null && naturalAbundance != null) return false;
  
          return true;
      }
docs: Compares an isotope with this isotope.
  
  @param  object Object of type Isotope
  @return        true if the isotopes are equal