code: public void placeHydrogens2D(final IAtomContainer container, final double bondLength) {
          logger.debug("placing hydrogens on all atoms");
          for (IAtom atom : container.atoms()) {
              // only place hydrogens for atoms which have coordinates
              if (atom.getPoint2d() != null) {
                  placeHydrogens2D(container, atom, bondLength);
              }
          }
          logger.debug("hydrogen placement complete");
      }
docs: Place all hydrogens connected to atoms which have already been laid out.
  
  @param container  atom container
  @param bondLength bond length to user