为什么不能在方法中本地声明枚举？

public double calculateTax(double income) {
    enum TaxBracket {
        BRACKET_1(0, 10000, 0.1),
        BRACKET_2(10001, 20000, 0.15),
        BRACKET_3(20001, 30000, 0.2),
        BRACKET_4(30001, Double.MAX_VALUE, 0.25);

        private final double min;
        private final double max;
        private final double rate;

        TaxBracket(double min, double max, double rate) {
            this.min = min;
            this.max = max;
            this.rate = rate;
        }

        public double getMin() {
            return min;
        }

        public double getMax() {
            return max;
        }

        public double getRate() {
            return rate;
        }
    }

    double tax = 0.0;
    for (TaxBracket bracket : TaxBracket.values()) {
        if (income > bracket.getMin() && income <= bracket.getMax()) {
            tax += (bracket.getMax() - bracket.getMin()) * bracket.getRate();
        }
    }

    return tax;
}