code: public static IAtomContainer convertExplicitToImplicitHydrogens(IAtomContainer atomContainer) {
          IAtomContainer mol = atomContainer.getBuilder().newInstance(IAtomContainer.class, atomContainer);
          convertImplicitToExplicitHydrogens(mol);
          if (mol.getAtomCount() > 1) {
              mol = removeHydrogens(mol);
          } else if (atomContainer.atoms().iterator().next().getSymbol().equalsIgnoreCase("H")) {
              System.err.println("WARNING: single hydrogen atom removal not supported!");
          }
          mol.addProperties(atomContainer.getProperties());
          mol.setFlags(atomContainer.getFlags());
          if (atomContainer.getID() != null) {
              mol.setID(atomContainer.getID());
          }
          return mol;
      }
docs: Returns IAtomContainer without Hydrogen. If an AtomContainer has atom single atom which
  is atom Hydrogen then its not removed.
  @param atomContainer
  @return IAtomContainer without Hydrogen. If an AtomContainer has atom single atom which
  is atom Hydrogen then its not removed.