随处可用的字符串、数字与集合
了解在所有目标平台上行为一致的核心标准库类型
随处可用的字符串、数字与集合 是 CoddyKit 上的免费 Kotlin Multiplatform Academy 课时。 这是第 1 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Kotlin Multiplatform Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Kotlin Multiplatform Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
One Toolbox, Every Target
The Kotlin stdlib ships with the language itself, so its core types behave the same on Android, iOS, desktop and beyond.
Strings Just Work
The String type is fully multiplatform. You can declare and combine text in commonMain and trust it everywhere.
val name: String = "Ada"
val hi = "Hello, " + nameString Helpers Travel With You
Handy String functions like uppercase, trim and length all live in common code, ready on each platform.
val tidy = " hi ".trim().uppercase()Numbers Are Shared Too
Number types such as Int, Long and Double are part of common Kotlin, so your math is identical across targets.
val total: Int = 2 + 3
val price: Double = 9.99Convert Between Types
Conversions like toInt and toDouble are common-safe, letting you reshape numbers anywhere your shared code runs.
val count = "42".toInt()
val ratio = count.toDouble()Meet the List
A List holds an ordered group of items. It is multiplatform, so the same collection powers both apps.
val fruits: List<String> = listOf("apple", "pear")Sets Keep Things Unique
A Set stores each value only once. Like List, it works the same way on every Kotlin target.
val tags: Set<String> = setOf("kmp", "kmp")Maps Pair Keys and Values
A Map links keys to values. It is fully shared, so lookups behave identically across all platforms.
val ages: Map<String, Int> = mapOf("Ada" to 36)Read Items Safely
Use indexing or getOrNull to read from a list. These collection operations are common-safe across targets.
val first = fruits[0]
val maybe = fruits.getOrNull(5)Why This Matters
Because these core types are identical everywhere, you write data logic once and never worry which platform runs it. 🙂
Default to Common Types
Reach for plain String, Int, List, Set and Map first. They are the safe, portable backbone of shared Kotlin.
Quick Check
Which collection fits this need?
Recap
Core stdlib types, String, numbers, List, Set and Map, behave the same on every target, so shared data logic is rock solid.
常见问题解答
「随处可用的字符串、数字与集合」课时是免费的吗？
是的 — 「随处可用的字符串、数字与集合」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Kotlin Multiplatform Academy 课程的其余内容，请升级到 CoddyKit PRO。 Kotlin Multiplatform Academy 课程共包含 4 节课。
「随处可用的字符串、数字与集合」这节课中我会学到什么？
了解在所有目标平台上行为一致的核心标准库类型 你通过在浏览器中直接运行的动手代码来练习 Kotlin Multiplatform Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Kotlin Multiplatform Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Kotlin Multiplatform Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 1 节课，共 4 节。
「随处可用的字符串、数字与集合」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Kotlin Multiplatform Academy 课中编写并运行代码吗？
能。每节 Kotlin Multiplatform Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。