code: @Nonnull
    public static String getConcatenatedOnDemand (@Nullable final String sFront, @Nullable final String sEnd)
    {
      if (sFront == null)
        return sEnd == null ? "" : sEnd;
      if (sEnd == null)
        return sFront;
      return sFront + sEnd;
    }
docs: Concatenate the strings sFront and sEnd. If either front or back is
  <code>null</code> or empty only the other element is returned. If both
  strings are <code>null</code> or empty and empty String is returned.
  
  @param sFront
  Front string. May be <code>null</code>.
  @param sEnd
  May be <code>null</code>.
  @return The concatenated string. Never <code>null</code>.