##和hashCode有什么区别? [英] What is the difference between `##` and `hashCode`?

问题描述

方法##和hashCode有什么区别?

无论我使用哪个类或hashCode重载，它们似乎都输出相同的值. Google也无济于事，因为它找不到符号##.

They seem to be outputting the same values no matter which class or hashCode overloading I use. Google doesn't help, either, as it cannot find symbol ##.

推荐答案

从散列的角度来看，AnyVal的子类"的行为不正确 :

"Subclasses" of AnyVal do not behave properly from a hashing perspective:

scala> 1.0.hashCode
res14: Int = 1072693248

当然，这是对以下人员的呼叫框:

Of course this is boxed to a call to:

scala> new java.lang.Double(1.0).hashCode
res16: Int = 1072693248

我们可能更愿意这样:

scala> new java.lang.Double(1.0).##
res17: Int = 1

scala> 1.0.##
res15: Int = 1

在int 1也是double 1的情况下，我们应该期望这一点.当然，在Java中不会出现此问题.没有它，我们会遇到这个问题:

We should expect this given that the int 1 is also the double 1. Of course this issue does not arise in Java. Without it, we'd have this problem:

Set(1.0) contains 1 //compiles but is false

幸运的是:

scala> Set(1.0) contains 1
res21: Boolean = true

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