Math.abs为Integer.Min_VALUE返回错误的值 [英] Math.abs returns wrong value for Integer.Min_VALUE

问题描述

此代码：

System.out.println(Math.abs(Integer.MIN_VALUE));

返回 -2147483648

它是否应该返回绝对值 2147483648 ？

Should it not return the absolute value as 2147483648 ?

推荐答案

Integer.MIN_VALUE 是 -2147483648 ，但最高值为32位整数可以包含 [phone] 。试图在32位int中表示 [phone] 将有效地翻转到 -2147483648 。这是因为，当使用有符号整数时， [phone] 和 -2147483648 的二进制补码表示相同。但是，这不是问题，因为 [phone] 被视为超出范围。

Integer.MIN_VALUE is -2147483648, but the highest value a 32 bit integer can contain is [phone]. Attempting to represent [phone] in a 32 bit int will effectively "roll over" to -2147483648. This is because, when using signed integers, the two's complement binary representations of [phone] and -2147483648 are identical. This is not a problem, however, as [phone] is considered out of range.

稍微阅读一点在这个问题上，你可能想查看维基百科有关二补的文章。

For a little more reading on this matter, you might want to check out the Wikipedia article on Two's complement.

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