return getFraction(denominator, numerator);
if (numerator==Integer.MIN_VALUE) { throw new ArithmeticException("overflow: can't negate numerator"); } if (numerator<0) { return new Fraction(-denominator, -numerator); } else { return new Fraction(denominator, numerator); }
    public Fraction invert() {        if (numerator == 0) {            throw new ArithmeticException("Unable to invert a fraction with a zero numerator");        }        return getFraction(denominator, numerator);    }