为什么在bigdecimal划分的0.454至0.5的圆形分区中会进行圆形模式。

发布于 2025-02-01 12:41:53 字数 1066 浏览 4 评论 0原文

圆形模式falt_even应该圆形a（十进制）数字以5结束至最接近的偶数的精确数字（例如，4.5舍入4.5，而5.5则是四舍五入的。到6）。

现在，Java的bigdecimal的部门似乎不遵守该规则。以下代码将其转到0.45至0.5：

import java.math.*;

class Round {
    public static void main(String[] args) {
        BigDecimal five = BigDecimal.valueOf(5);
        BigDecimal eleven = BigDecimal.valueOf(11);
        BigDecimal x = five.divide(eleven, 1, RoundingMode.HALF_EVEN);
        System.out.println(x);
    }
}

输出0.5 请注意，5/11 = 0.4545454545 ...因此，当查看小数点后的前两个数字时，0.45，我们显然希望看到它被舍入到最近的邻居，即IE，即0.40，而不是0.50。

谁能解释一下？

（如果很重要，我正在运行java -version = openjdk版本“ 11.0.15” 2022-04-19）

注意：

这不是关于在之前 大数的价值；的确当使用字符串构造函数时，结果也没有变化，

     BigDecimal five = new BigDecimal("5");
     BigDecimal eleven = new BigDecimal("11");
     BigDecimal x = five.divide(eleven, 1, RoundingMode.HALF_EVEN);

它也不取决于我们圆形的比例（只要尺度为奇数），并且您可以将数字扩展到数字（例如，循环500/11）。

原文

The rounding mode HALF_EVEN is supposed to round a (decimal) number ending in 5 to the closest even less precise number (e.g., 4.5 is rounded to 4, whereas 5.5 is rounded to 6).

Now, it seems that Java's division of BigDecimal is not obeying that rule; the following code gets it to round 0.45 to 0.5:

import java.math.*;

class Round {
    public static void main(String[] args) {
        BigDecimal five = BigDecimal.valueOf(5);
        BigDecimal eleven = BigDecimal.valueOf(11);
        BigDecimal x = five.divide(eleven, 1, RoundingMode.HALF_EVEN);
        System.out.println(x);
    }
}

Output 0.5
Note that 5/11 = 0.4545454545... so when looking at the first two digits after the decimal point, 0.45, we clearly would want to see that rounded to the nearest even neighbor, i.e. to 0.40, not 0.50.

Can anyone explain this?

(In case it matters, I'm running java -version = openjdk version "11.0.15" 2022-04-19)

Note:

This is not about rounding before getting a value into the BigDecimal; indeed
the result is unchanged when using the string constructor

     BigDecimal five = new BigDecimal("5");
     BigDecimal eleven = new BigDecimal("11");
     BigDecimal x = five.divide(eleven, 1, RoundingMode.HALF_EVEN);