code: public static String join(final String sep, final Iterable<?> iterable) {
          final StringBuilder buf = new StringBuilder();
          join(buf, "", sep, "", iterable);
          return buf.toString();
      }
docs: A replacement for Java 8's String.join().
  
  @param sep
  The separator string.
  @param iterable
  The {@link Iterable} to join.
  @return The string representation of the joined elements.