为什么Kotlin使用诸如arrayOf之类的全局函数 [英] Why does Kotlin use global functions like arrayOf

问题描述

我是Kotlin的新手.我发现这是一种怪异的做法.

I'm new to Kotlin. I find this to be a weird practice.

在arrayOf/mutableListOf的情况下，本能是尝试使用构造函数(即new Array<T>(...args))尝试这些类型之一的 construct .甚至是静态工厂方法，例如LocalDateTime.of(...).

With the case of arrayOf / mutableListOf, the instinct is to try a construct one of these types using a constructor, i.e. new Array<T>(...args). Or even a static factory method, like i.e. LocalDateTime.of(...).

为什么不使用new Array<T>()，或者至少不使用范围函数，即Array.of.这些方法也不会使全局范围杂乱无章吗?

Why wasn't new Array<T>() used, or at least a scoped function, i.e. Array.of. Don't these methods also clutter the global scope?

推荐答案

arrayOf和mutableListOf不在全局范围"内(甚至不存在).它们分别位于kotlin和kotlin.collections软件包中.

arrayOf and mutableListOf are not in "global scope" (that's not even something that exists). They're in the kotlin and kotlin.collections packages, respectively.

kotlin.*和kotlin.collections.*恰好是任何kotlin文件的默认导入，因此您不必自己进行该导入.请参见默认导入.

It just so happens that kotlin.* and kotlin.collections.* are default imports of any kotlin file, so you don't have to make that import yourself. See Default Imports.

这类似于Java，其中默认情况下会导入java.lang.*，而无需指定它.

This is similar to Java where java.lang.* is imported by default and you don't need to specify it.

此外，您不能构造" arrayOf和mutableListOf，因为它们不是类型.它们是方法-实际上，它们以小写字母开头是表明类型的标准方式-类型以大写字母开头.

Also, you can't "construct" arrayOf and mutableListOf because they're not types; they're methods - and the fact the they start with a lowercase letter is the standard way to indicate that - types start with uppercase letters.

Kotlin允许类级别以外的程序包级别的方法(尽管为JVM编译时，它们将位于类内部)，但这与Java中的import static并没有太大区别，在Java中，import static可以从其中访问静态方法.没有类名作为前缀的类.

Kotlin allows methods at package level outside a class (although when compiled for the JVM, they will be inside a class), but that's not very different from an import static in Java with which you can access a static method from a class without the classname as a prefix.

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