code: public static String asPath(final String... strings) {
          if (strings == null) return null;
          final StringBuilder bldr = new StringBuilder();
          for (final String string : strings) {
              if (bldr.length() != 0) bldr.append(separator);
              bldr.append(string);
          }
          return bldr.toString();
      }
docs: Inserts the platform-specific filesystem path separator between the
  provided strings.
  
  @param strings
  @return String in the following form:
  {@code strings[0]<path_separator>strings[1]<path_separator>...<strings[n]>}
  , or <b>null</b> if {@code strings} is null