code: public static <T> String join(Iterable<T> iterable) {
          dbc.precondition(iterable != null, "cannot join a null iterable");
          return new JoinStrings<T>().apply(iterable.iterator());
      }
docs: Joins an iterable of T into a String. E.g: <code>[1,2,3] -> "123"</code>
  
  @param <T> the iterable element type
  @param iterable the iterable to be joined
  @return the resulting string