如何使用“x< = y& amp;& x> = y&& x！= y"？ [英] How to make loop infinite with "x <= y && x >= y && x != y"?

问题描述

几年前我有这个面试问题，但我还没有找到答案。

I had this interview question some years ago but I haven't found the answer yet.

x和y应该是什么才能产生无限循环？

What should be x and y to make a infinite loop?

while (x <= y&& x >= y && x != y) {

}

我们试过 Nan ，无穷大+/- ， null

float vs int 。

推荐答案

您需要两个可比较的变量，具有相同的值，但代表不同的实例，例如：

You need two variables which are comparable, have the same value, but represent different instances, for example:

Integer x = new Integer(0);
Integer y = new Integer(0);

x< = y 和 y< = x 都是true，因为 Integer 是未装箱的，但是实例相等 x = = y 为假。

x <= y and y <= x are both true because the Integer are unboxed, however the instance equality x == y is false.

请注意，它适用于 Float ，长和 Double ，任何值（不只是0）都有效。

Note that it works with Float, Long and Double too, and any value (not just 0) works.

您还可以使用JVM的复杂性 - 它们通常只缓存最多127个整数，所以这也可以：

You can also play with the intricacies of your JVM - they generally cache integer up to 127 only, so this would work too:

Integer x = 128;
Integer y = 128;

（但不会是127）。

或者更简单，因为 Double s通常根本不缓存：

Or more simply, since Doubles are generally not cached at all:

Double x = 0d;
Double y = 0d;

这篇关于如何使用“x< = y& amp;& x> = y&& x！= y"？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！