code: public static String concat(Iterable<String> iterable) {
          dbc.precondition(iterable != null, "cannot concat a null iterable");
          return new ConcatStrings().apply(iterable.iterator());
      }
docs: Concatenate an iterable of Strings into a single String. E.g: <code>["1","2","3"] -> "123"</code>
  
  @param iterable the iterable to be concatenated
  @return the resulting string