code: @Override
  	public boolean isEmpty() {
  		if (getStart() != null && getStart().isNaN())
  			return true;
  		if (getEnd() != null && getEnd().isNaN())
  			return true;
  		if (getStart() != null && getEnd() != null) {
  			if (getStart() == Double.POSITIVE_INFINITY && getEnd() == Double.POSITIVE_INFINITY)
  				return true;
  			if (getStart() == Double.NEGATIVE_INFINITY && getEnd() == Double.NEGATIVE_INFINITY)
  				return true;
  		}
  		return super.isEmpty();
  	}
docs: Determines if the interval is empty, meaning it contains no Doubles. Unlike the class
  {@link IntegerInterval}, the interval (4.0, 5.0), for example, will <strong>not</strong>
  be considered empty, because there are Double values in this interval.
  <p>
  If the start or end point of the interval is Double.NaN, the interval will be
  considered empty.
  </p>
  @return