code: @Override
      public DescriptorValue calculate(IAtomContainer container) {
  
          double bpol = 0;
          int atomicNumber0;
          int atomicNumber1;
          double difference;
          try {
              IsotopeFactory ifac = Isotopes.getInstance();
              IElement element0;
              IElement element1;
  
              String symbol0;
              String symbol1;
              for (IBond bond : container.bonds()) {
                  IAtom atom0 = bond.getBegin();
                  IAtom atom1 = bond.getEnd();
  
                  symbol0 = atom0.getSymbol();
                  symbol1 = atom1.getSymbol();
                  element0 = ifac.getElement(symbol0);
                  element1 = ifac.getElement(symbol1);
                  atomicNumber0 = element0.getAtomicNumber();
                  atomicNumber1 = element1.getAtomicNumber();
                  difference = polarizabilities[atomicNumber0] - polarizabilities[atomicNumber1];
                  bpol += Math.abs(difference);
              }
  
              // after going through the bonds, we go through the atoms and see if they have
              // implicit H's and if so, consider the associated "implicit" bonds. Note that
              // if the count is UNSET, we assume it is 0
              for (IAtom atom : container.atoms()) {
                  int impH = atom.getImplicitHydrogenCount() == CDKConstants.UNSET ? 0 : atom.getImplicitHydrogenCount();
                  IElement elem = ifac.getElement(atom.getSymbol());
                  int atnum = elem.getAtomicNumber();
                  difference = Math.abs(polarizabilities[atnum] - polarizabilities[1]) * impH;
                  bpol += difference;
              }
              return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(),
                      new DoubleResult(bpol), getDescriptorNames());
          } catch (Exception ex1) {
              logger.debug(ex1);
              return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(), new DoubleResult(
                      Double.NaN), getDescriptorNames(), new CDKException("Problems with IsotopeFactory due to "
                      + ex1.toString(), ex1));
          }
      }
docs: This method calculate the sum of the absolute value of
  the difference between atomic polarizabilities of all bonded atoms in the molecule
  
  @param  container  Parameter is the atom container.
  @return            The sum of atomic polarizabilities