code: public static String format(int[] a, String sep) {
      return (a == null) ? "null" : (a.length == 0) ? "" : //
          formatTo(new StringBuilder(), a, sep).toString();
    }
docs: Formats the int array a for printing purposes.
  
  @param a the int array to be formatted
  @param sep the separator between the single values of the array, e.g. ','
  @return a String representing the int array a