BigDecimal 加减乘除 比较大小 取余 mod

加减乘除

        BigDecimal a = new BigDecimal("1");
        BigDecimal b = new BigDecimal("3");
        BigDecimal c = a.add(b);
        BigDecimal d = a.subtract(b);
        BigDecimal e = a.multiply(b);
        BigDecimal f = a.divide(b,2,BigDecimal.ROUND_HALF_UP);
        System.out.println(c);
        System.out.println(d);
        System.out.println(e);
        System.out.println(f);

a.compareTo(b)

        BigDecimal[] mod = a.divideAndRemainder(b);
        BigDecimal mod0 = mod[0];
        BigDecimal mod1 = mod[1];
        System.out.println(mod0);
        System.out.println(mod1);

小数： 

        BigDecimal h = new BigDecimal("1.23456789");
        h.setScale(1,BigDecimal.ROUND_DOWN);//直接删除多余的小数位，如1.2
        h.setScale(1,BigDecimal.ROUND_UP);//进位处理，1.3
        h.setScale(3,BigDecimal.ROUND_HALF_UP);//四舍五入(5则向上入)，1.235
        h.setScale(3,BigDecimal.ROUND_HALF_DOWN);//五舍六入(5则向下舍，6则向上入)，1.234

Exception in thread "main" java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.