code: public static double calculateAverageBondLength(IReaction reaction) {
  
          IAtomContainerSet reactants = reaction.getReactants();
          double reactantAverage = 0.0;
          if (reactants != null) {
              reactantAverage = calculateAverageBondLength(reactants) / reactants.getAtomContainerCount();
          }
  
          IAtomContainerSet products = reaction.getProducts();
          double productAverage = 0.0;
          if (products != null) {
              productAverage = calculateAverageBondLength(products) / products.getAtomContainerCount();
          }
  
          if (productAverage == 0.0 && reactantAverage == 0.0) {
              return 1.0;
          } else {
              return (productAverage + reactantAverage) / 2.0;
          }
      }
docs: Calculate the average bond length for the bonds in a reaction.
  
  @param reaction the reaction to use
  @return the average bond length