code: public static <E extends Comparable<E>> Interval<E> toInterval(E a, E b) {
      return toInterval(a,b,0);
    }
docs: Create an interval with the specified endpoints in the specified order,
  Returns null if a does not come before b (invalid interval)
  @param a start endpoints
  @param b end endpoint
  @param <E> type of the interval endpoints
  @return Interval with endpoints in specified order, null if a does not come before b