Float直接轉BigDecimal會導致精度丟失，得先轉成String 再轉BigDecimal

    @Test
    public void test17() {
        Float f = 12.635f;
        System.out.println(new BigDecimal(f));
        BigDecimal mon = new BigDecimal(Float.toString(f));
        System.out.println(mon);
    }