为什么使用 Collection.empty[T] 而不是 new Collection[T]() [英] Why use Collection.empty[T] instead of new Collection[T]()

问题描述

我想知道是否有充分的理由使用 Collection.empty[T] 而不是 new Collection[T]()(或相反)?还是只是个人喜好?

I was wondering if there is a good reason to use Collection.empty[T] instead of new Collection[T]() (or the inverse) ? Or is it just a personal preference ?

谢谢.

推荐答案

调用 new Collection[T]() 每次都会创建一个新实例.另一方面，Collection.empty[T] 很可能总是返回相同的单例 object，通常在某处定义为

Calling new Collection[T]() will create a new instance every time. On the other hand, Collection.empty[T] will most likely always return the same singleton object, usually defined somewhere as

object Empty extends Collection[Nothing] ...

这会快得多.这仅适用于不可变集合，每次调用 empty 时，可变集合都必须返回一个新实例.

which will be much faster. This is only possible for immutable collections, mutable collections have to return a new instance every time empty is called.

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