code: @Override
      public IReactionSet initiate(IAtomContainerSet reactants, IAtomContainerSet agents) throws CDKException {
  
          logger.debug("initiate reaction: ElectronImpactNBEReaction");
  
          if (reactants.getAtomContainerCount() != 1) {
              throw new CDKException("ElectronImpactNBEReaction only expects one reactant");
          }
          if (agents != null) {
              throw new CDKException("ElectronImpactNBEReaction don't expects agents");
          }
  
          IReactionSet setOfReactions = reactants.getBuilder().newInstance(IReactionSet.class);
          IAtomContainer reactant = reactants.getAtomContainer(0);
  
          /*
           * if the parameter hasActiveCenter is not fixed yet, set the active
           * centers
           */
          IParameterReact ipr = super.getParameterClass(SetReactionCenter.class);
          if (ipr != null && !ipr.isSetParameter()) setActiveCenters(reactant);
  
          Iterator<IAtom> atoms = reactant.atoms().iterator();
          while (atoms.hasNext()) {
              IAtom atom = atoms.next();
              if (atom.getFlag(CDKConstants.REACTIVE_CENTER) && reactant.getConnectedLonePairsCount(atom) > 0
                      && reactant.getConnectedSingleElectronsCount(atom) == 0) {
  
                  ArrayList<IAtom> atomList = new ArrayList<IAtom>();
                  atomList.add(atom);
                  IAtomContainerSet moleculeSet = reactant.getBuilder().newInstance(IAtomContainerSet.class);
                  moleculeSet.addAtomContainer(reactant);
                  IReaction reaction = mechanism.initiate(moleculeSet, atomList, null);
                  if (reaction == null)
                      continue;
                  else
                      setOfReactions.addReaction(reaction);
              }
          }
          return setOfReactions;
  
      }
docs: Initiate process.
  It is needed to call the addExplicitHydrogensToSatisfyValency
  from the class tools.HydrogenAdder.
  
  
  @param  reactants         Reactants of the reaction
  @param  agents            Agents of the reaction (Must be in this case null)
  
  @exception  CDKException  Description of the Exception