为什么 null.asInstanceOf[Int] 不抛出 NullPointerException? [英] why doesn't null.asInstanceOf[Int] throw a NullPointerException?

问题描述

由于 Int不符合"AnyRef，我不确定它为什么不根据 Scala 参考 6.3 节:

Since Int "does not conform to" AnyRef, I am not sure why it doesn't throw a NullPointerException according to Scala Reference on Section 6.3 :

asInstanceOf[T ] 如果 T 符合scala.AnyRef，否则抛出 NullPointerException

asInstanceOf[T ] returns the "null" object itself if T conforms to scala.AnyRef, and throws a NullPointerException otherwise

null.asInstanceOf[Double]、null.asInstanceOf[Boolean]、null.asInstanceOf[Char] 也没有.

PS:我的 Scala 库是 2.9.0.1 版和 OS Windows XP

PS: My scala library is of version 2.9.0.1 and OS windows XP

推荐答案

在 Scala 中 Null 是一种类型，它只有一个值 null.由于 null 是一个值，Scala 中的每个值都是一个对象，因此您可以对其调用方法.

In Scala Null is a type, which has a single value null. Since null is a value and every value in Scala is an object, you can call methods on it.

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