code: @Override
      public void addAtom(IAtom oAtom, IMonomer oMonomer) {
  
          if (!contains(oAtom)) {
              super.addAtom(oAtom);
  
              if (oMonomer != null) { // Not sure what's better here...throw nullpointer exception?
                  oMonomer.addAtom(oAtom);
                  if (!monomers.containsKey(oMonomer.getMonomerName())) {
                      monomers.put(oMonomer.getMonomerName(), oMonomer);
                  }
              }
          }
          /*
           * notifyChanged() is called by addAtom in AtomContainer
           */
      }
docs: Adds the atom oAtom to a specified Monomer.
  
  @param oAtom  The atom to add
  @param oMonomer  The monomer the atom belongs to