code: public static String join(String[] collection, String separator,
                                boolean trailing) {
          return join(Arrays.asList(collection), separator, trailing);
      }
docs: Join an array of strings with a separator that appears after every
  instance in the list -optionally at the end
  
  @param collection strings
  @param separator  separator string
  @param trailing   add a trailing entry or not
  @return the joined entries