如何在Kotlin中将List转换为Map? [英] How to convert List to Map in Kotlin?

问题描述

例如，我有一个字符串列表，如:

For example I have a list of strings like:

val list = listOf("a", "b", "c", "d")

我想将其转换为以字符串为键的映射.

and I want to convert it to a map, where the strings are the keys.

我知道我应该使用.toMap()函数，但是我不知道如何使用它，并且我还没有看到它的任何示例.

I know I should use the .toMap() function, but I don't know how, and I haven't seen any examples of it.

推荐答案

您有两种选择:

最有效的方法是使用associateBy函数，该函数需要两个lambda来生成键和值，并内联地图的创建:

The first and most performant is to use associateBy function that takes two lambdas for generating the key and value, and inlines the creation of the map:

val map = friends.associateBy({it.facebookId}, {it.points})

第二个效果较差的方法是使用标准map函数创建Pair列表，toMap可以使用该列表生成最终地图:

The second, less performant, is to use the standard map function to create a list of Pair which can be used by toMap to generate the final map:

val map = friends.map { it.facebookId to it.points }.toMap()

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