java - 如何否定一个值与java [Integer.Min_Value]中的值相同

Question

这些值在 java 中如何相同？

-Integer.MIN_VALUE == Integer.MIN_VALUE

值是:

-2147483648 : -2147483648

我尝试比较它并返回 true [太棒了!]

Answer 1

是的，这是预期的行为。 int的范围是 -2147483648 到 +2147483647。

来自JLS section 15.15.4 (强调我的):

For integer values, negation is the same as subtraction from zero. The Java programming language uses two's-complement representation for integers, and the range of two's-complement values is not symmetric, so negation of the maximum negative int or long results in that same maximum negative number. Overflow occurs in this case, but no exception is thrown. For all integer values x, -x equals (~x)+1.

~Integer.MIN_VALUE是Integer.MAX_VALUE ...当您添加一个时，它会溢出到 Integer.MIN_VALUE .

这就是为什么在实现反向比较器时，您绝不能这样做:

// BAD CODE!
public int compare(T x, T y) {
    return -originalComparator.compare(x, y);
}

相反，使用这个:

// This is fine, assuming the comparator obeys its contract
public int compare(T x, T y) {
    return originalComparator.compare(y, x));
}