Java - List<Integer> 排序、比较器和溢出

Question

我有以下代码按降序对列表进行排序

List<Integer> list=Arrays.asList(Integer.MAX_VALUE, -1);
list.sort((x, y) -> y-x);
System.out.println(list)

结果是

[-1, 2147483647]

现在，我知道我不应该写 y-x，因为它会导致溢出问题。

但问题是为什么输出是这样的？我相信输出会是 [2147483647, -1] 因为 -1 - Integer.MAX_VALUE 是 -2147483648，仍然是一个负整数，广告该操作似乎不受溢出问题的影响。 我做错了什么？

Answer 1

正如您在 Oracle's Object Ordening Java Tutorial 中所读到的那样靠近页面底部:

You might be tempted to replace the final return statement in the Comparator with the simpler:

return e1.number() - e2.number(); 

Don't do it unless you're absolutely sure no one will ever have a negative employee number! This trick does not work in general because the signed integer type is not big enough to represent the difference of two arbitrary signed integers. If i is a large positive integer and j is a large negative integer, i - j will overflow and will return a negative integer. The resulting comparator violates one of the four technical restrictions we keep talking about (transitivity) and produces horrible, subtle bugs. This is not a purely theoretical concern; people get burned by it.

这里描述的情况是OP遇到的情况:两个整数之间的差值大于Integer.MAX_VALUE，因此在比较时会溢出，导致意外排序。