diff --git a/README.md b/README.md index 4cc59fd..46c52aa 100644 --- a/README.md +++ b/README.md @@ -9,7 +9,7 @@ Quick Reference -[![Quick Reference](https://user-images.githubusercontent.com/1680273/200623638-280ac85b-0cfa-4c60-bae3-ae14231acc6f.png)](https://jaywcjlove.github.io/reference) +[![Quick Reference](https://user-images.githubusercontent.com/1680273/201931931-d8559417-0a15-46af-a009-ec1e56e5b778.png)](https://jaywcjlove.github.io/reference) 为开发人员分享快速参考备忘清单【速查表】。在看到 [Reference](https://github.com/Randy8080/reference) 快速参考备忘单，感觉非常简单，造中文版本的轮子使命感突然来了，为了方便自己的技术栈查阅，如果您提供一个清单，我将抽空搬运，立即撸起来 :)。如果您发现此处的备忘单不合适，您可以通过提交 [PR](https://github.com/jaywcjlove/reference/blob/main/CONTRIBUTING.md) 来修复它或提供更好的备忘清单，只针对【中文】用户。以下是开源天使提供的一些备忘清单和快速参考 :)。 @@ -44,6 +44,7 @@ Quick Reference [JSON](./docs/json.md) [Java](./docs/java.md) [Julia](./docs/julia.md) +[Kotlin](./docs/kotlin.md) [LaTeX](./docs/latex.md) [Markdown](./docs/markdown.md) [MySQL](./docs/mysql.md) diff --git a/docs/kotlin.md b/docs/kotlin.md new file mode 100644 index 0000000..b5875aa --- /dev/null +++ b/docs/kotlin.md @@ -0,0 +1,718 @@ +Kotlin 备忘清单 +=== + +Kotlin 备忘清单是 [Kotlin](https://kotlinlang.org) 编程语言的单页参考表 + +Kotlin 简介 +---- + +### main() 函数 + +```kotlin +fun main() { + // Code goes here +} +``` + +main() 函数是每个 Kotlin 程序的起点，在执行之前必须包含在代码中 + +### 打印声明 + +```kotlin +println("Greetings, earthling!") +print("Take me to ") +print("your leader.") + +/* +打印: +Greetings, earthling! +Take me to your leader. +*/ +``` + +### 注释 + +```kotlin +// 这是单行注释 + +/* +这个 +注释 +用于 +多 +行 +*/ +``` + +### 执行顺序 + +```kotlin +fun main() { + println("I will be printed first.") + println("I will be printed second.") + println("I will be printed third.") +} +``` + +数据类型和变量 +--- + +### 可变变量 + +```kotlin +var age = 25 +age = 26 +``` + +### 不可变变量 + +```kotlin +val goldenRatio = 1.618 +``` + +### 类型推断 + +```kotlin +// 以下变量在双引号内分配了一个文本值 +// 因此推断的类型是 String + +var color = "Purple" +``` + +### 字符串连接 + +```kotlin +var streetAddress = "123 Main St." +var cityState = "Brooklyn, NY" + +println(streetAddress + " " + cityState) +// 打印: 123 Main St. Brooklyn, NY +``` + +### 字符串模板 + +```kotlin +var address = "123 Main St." +println("The address is $address") +// 打印: The address is 123 Main St. +``` + +### 内置属性和函数 + +```kotlin +var monument = "the Statue of Liberty" + +println(monument.capitalize()) +// 打印: The Statue of Liberty +println(monument.length) +// 打印: 21 +``` + +### 字符转义序列 + + +```kotlin +print("\"Excellent!\" I cried. \"Elementary,\" said he.") + +// 打印: "Excellent!" I cried. "Elementary," said he. +``` + + +- `\n` 插入新行 +- `\t` 插入标签 +- `\r` 插入回车 +- `\'` 插入单引号 +- `\"` 插入双引号 +- `\\` 插入反斜杠 +- `\$` 插入美元符号 + +### 算术运算符 + +```kotlin +5 + 7 // 12 +9 - 2 // 7 +8 * 4 // 32 +25 / 5 // 5 +31 % 2 // 1 +``` + +`+` 加法、`-` 减法、`*` 乘法、`/` 除法和 `%` 模数 + +### 操作顺序 + +```kotlin +5 + 8 * 2 / 4 - 3 // 6 +3 + (4 + 4) / 2 // 7 +4 * 2 + 1 * 7 // 15 +3 + 18 / 2 * 1 // 12 +6 - 3 % 2 + 2 // 7 +``` + +### 增强赋值运算符 + +```kotlin +var batteryPercentage = 80 + +// 长语法 +batteryPercentage = batteryPercantage + 10 + +// 带有增广赋值运算符的短句法 +batteryPercentage += 10 +``` + +### 递增和递减运算符 + +```kotlin +var year = 2019 +year++ // 2020 +year-- // 2019 +``` + +### 数学库 + +```kotlin +Math.pow(2.0, 3.0) // 8.0 +Math.min(6, 9) // 6 +Math.max(10, 12) // 12 +Math.round(13.7) // 14 +``` + +条件表达式 +---- + +### if 表达式 + +```kotlin +var morning = true + +if (morning) { + println("Rise and shine!") +} +// 打印: Rise and shine! +``` + +### else 表达式 + +```kotlin +var rained = false + +if (rained) { + println("今天不需要给植物浇水。") +} else { + println("植物需要浇水！") +} +// 打印: 植物需要浇水！ +``` + +### Else-If 表达式 + +```kotlin +var age = 65 + +if (age < 18 ) { + println("您被视为未成年人") +} else if (age < 60) { + println("您被视为成年人") +} else { + println("你被认为是高级") +} + +// 打印: 你被认为是高级 +``` + +### 比较运算符 + +```kotlin +var myAge = 19 +var sisterAge = 11 +var cousinAge = 11 + +myAge > sisterAge // true +myAge < cousinAge // false +myAge >= cousinAge // true +myAge <= sisterAge // false +``` + +### 逻辑运算符 + +```kotlin +var humid = true +var raining = true +var jacket = false + +println(!humid) +// 打印: false +println(jacket && raining) +// 打印: true +println(humid || raining) +// 打印: true +``` + +### AND 运算符： && + +```kotlin +var humid = true +var raining = true +var shorts = false +var sunny = false + +// true AND true +println(humid && raining) // true +// true AND false +println(humid && shorts) // false +// false AND true +println(sunny && raining) // false +// false AND false +println(shorts && sunny) // false +``` + +### 或运算符：|| + +```kotlin +var late = true +var skipBreakfast = true +var underslept = false +var checkEmails = false + +// true OR true +println(skipBreakfast || late) // true +// true OR false +println(late || checkEmails) // true +// false OR true +println(underslept || late) // true +// false OR false +println(checkEmails || underslept) // false +``` + +### NOT 运算符 + +```kotlin +var hungry = true +var full = false + +println(!hungry) // false +println(!full) // true +``` + +### 评估顺序 + +```kotlin +!true && (false || true) // false +/* +(false || true) 被评估首先返回 true。 +然后，评估 !true && true 并返回最终结果 false +*/ + +!false && true || false // true +/* +!false 被评估首先返回 true。 +然后评估 true && true，返回 true。 +那么，真|| 评估 false 最终返回 true +*/ +``` + +### 嵌套条件 + +```kotlin +var studied = true +var wellRested = true + +if (wellRested) { + println("祝你今天好运！") + if (studied) { + println("你应该为考试做好准备！") + } else { + println("考试前花几个小时学习！") + } +} + +// 打印: 祝你今天好运！ +// 打印: 你应该为考试做好准备！ +``` + +### 当表达式 + +```kotlin +var grade = "A" + +when(grade) { + "A" -> println("很棒的工作！") + "B" -> println("做得太好了！") + "C" -> println("你通过了！") + else -> println("关！下次一定要多准备！") +} +// 打印: 很棒的工作！ +``` + +### 范围运算符 + +```kotlin +var height = 46 // inches + +if (height in 1..53) { + println("抱歉，您必须至少 54 英寸才能乘坐过山车"） +} +// Prints: 抱歉，您必须至少 54 英寸才能乘坐过山车 +``` + + +### 等式运算符 + +```kotlin +var myAge = 22 +var sisterAge = 21 + +myAge == sisterAge // false +myAge !== sisterAge // true +``` + +Collections +--- + +### 不可变列表 + +```kotlin +var programmingLanguages = listOf("C#", "Java", "Kotlin", "Ruby") +``` + + +### 可变列表 + +```kotlin +var fruits = mutableListOf("Orange", "Apple", "Banana", "Mango") +``` + + +### 访问列表元素 + +```kotlin +var cars = listOf("BMW", "Ferrari", "Volvo", "Tesla") + +println(cars[2]) // Prints: Volvo +``` + + +### 大小属性 + +```kotlin +var worldContinents = listOf("Asia", "Africa", "North America", "South America", "Antarctica", "Europe", "Australia") + +println(worldContinents.size) // Prints: 7 +``` + + +### 列表操作 + + +```kotlin +var seas = listOf("Black Sea", "Caribbean Sea", "North Sea") +println(seas.contains("North Sea")) // Prints: true + +// contains() 函数对任何列表执行读取操作并确定元素是否存在 +seas.add("Baltic Sea") // 错误：无法对不可变列表执行写操作 +// add() 函数只能在可变列表上调用，因此上面的代码会引发错误 +``` + + +### 不可变集 + +```kotlin +var primaryColors = setOf("Red", "Blue", "Yellow") +``` + + +### 可变集 + +```kotlin +var womenInTech = mutableSetOf("Ada Lovelace", "Grace Hopper", "Radia Perlman", "Sister Mary Kenneth Keller") +``` + + +### 访问集合元素 + + +```kotlin +var companies = setOf("Facebook", "Apple", "Netflix", "Google") + +println(companies.elementAt(3)) +// Prints: Google +println(companies.elementAt(4)) +// Returns and Error +println(companies.elementAtOrNull(4)) +// Prints: null +``` + + +### 不可变映射 + +```kotlin +var averageTemp = mapOf("winter" to 35, "spring" to 60, "summer" to 85, "fall" to 55) +``` + + +### 可变映射 + +```kotlin +var europeanDomains = mutableMapOf("Germany" to "de", "Slovakia" to "sk", "Hungary" to "hu", "Norway" to "no") +``` + + +### 检索映射键和值 + +```kotlin +var oscarWinners = mutableMapOf("Parasite" to "Bong Joon-ho", "Green Book" to "Jim Burke", "The Shape Of Water" to "Guillermo del Toro") + +println(oscarWinners.keys) +// Prints: [Parasite, Green Book, The Shape Of Water] + +println(oscarWinners.values) +// Prints: [Bong Joon-ho, Jim Burke, Guillermo del Toro] + +println(oscarWinners["Parasite"]) +// Prints: Bong Joon-ho +``` + + +### 添加和删除地图条目 + +```kotlin +var worldCapitals = mutableMapOf("United States" to "Washington D.C.", "Germany" to "Berlin", "Mexico" to "Mexico City", "France" to "Paris") + +worldCapitals.put("Brazil", "Brasilia") +println(worldCapitals) +// Prints: {United States=Washington D.C., Germany=Berlin, Mexico=Mexico City, France=Paris, Brazil=Brasilia} + +worldCapitals.remove("Germany") +println(worldCapitals) +// Prints: {United States=Washington D.C., Mexico=Mexico City, France=Paris, Brazil=Brasilia} +``` + + +函数 +--- + +### 函数 + +```kotlin +fun greet() { + println("Hey there!") +} + +fun main() { + // Function call + greet() // Prints: Hey there! +} +``` + +### 函数参数 + +```kotlin +fun birthday(name: String, age: Int) { + println("Happy birthday $name! You turn $age today!") +} + +fun main() { + birthday("Oscar", 26) + // Prints: Happy birthday Oscar! You turn 25 today! + birthday("Amarah", 30) + // Prints: Happy birthday Amarah! You turn 30 today! +} +``` + + +### 默认参数 + +```kotlin +fun favoriteLanguage(name, language = "Kotlin") { + println("Hello, $name. Your favorite programming language is $language") +} + +fun main() { + favoriteLanguage("Manon") + // Prints: Hello, Manon. Your favorite programming language is Kotlin + + favoriteLanguage("Lee", "Java") + // Prints: Hello, Lee. Your favorite programming language is Java +} +``` + + +### 命名参数 + +```kotlin +fun findMyAge(currentYear: Int, birthYear: Int) { + var myAge = currentYear - birthYear + println("I am $myAge years old.") +} + +fun main() { + findMyAge(currentYear = 2020, birthYear = 1995) + // Prints: I am 25 years old. + findMyAge(birthYear = 1920, currentYear = 2020) + // Prints: I am 100 years old. +} +``` + + +### 返回声明 + +```kotlin +// Return type is declared outside the parentheses +fun getArea(length: Int, width: Int): Int { + var area = length * width + + // return statement + return area +} + +fun main() { + var myArea = getArea(10, 8) + println("The area is $myArea.") + // Prints: The area is 80. +} +``` + + +### 单表达式函数 + +```kotlin +fun fullName(firstName: String, lastName: String) = "$firstName $lastName" + +fun main() { + println(fullName("Ariana", "Ortega")) + // Prints: Ariana Ortega + println(fullName("Kai", "Gittens")) + // Prints: Kai Gittens +} +``` + + +### 函数字面量 + +```kotlin +fun main() { + // Anonymous Function: + var getProduct = fun(num1: Int, num2: Int): Int { + return num1 * num2 + } + println(getProduct(8, 3)) + // Prints: 24 + + // Lambda Expression + var getDifference = { num1: Int, num2: Int -> num1 - num2 } + println(getDifference(10, 3)) + // Prints: 7 +} +``` + + +类 +--- + +### 类示例 + +```kotlin +// 具有包含默认值的属性的类 +class Student { + var name = "Lucia" + var semester = "Fall" + var gpa = 3.95 +} + +// 没有类体的简写语法 +class Student +``` + +### 类实例 + +```kotlin +// Class +class Student { + var name = "Lucia" + var semester = "Fall" + var gpa = 3.95 +} + +fun main() { + var student = Student() + // Instance + println(student.name) + // Prints: Lucia + println(student.semester) + // Prints: Fall + println(student.gpa) + // Prints: 3.95 +} +``` + +### 主构造函数 + +```kotlin +class Student(val name: String, val gpa: Double, val semester: String, val estimatedGraduationYear: Int) + +fun main() { + var student = Student("Lucia", 3.95, "Fall", 2022) + println(student.name) + // Prints: Lucia + println(student.gpa) + // Prints: 3.95 + println(student.semester) + // Prints: Fall + println(student.estimatedGraduationYear) + // Prints: 2022 +} +``` + + +### 初始化块 + +```kotlin +class Student(val name: String, val gpa: Double, val semester: String, val estimatedGraduationYear: Int) { + init { + println("$name has ${estimatedGraduationYear - 2020} years left in college.") + } +} + +fun main() { + var student = Student("Lucia", 3.95, "Fall", 2022) + // Prints: Lucia has 2 years left in college. +} +``` + + +### 成员函数 + + +```kotlin +class Student(val name: String, val gpa: Double, val semester: String, val estimatedGraduationYear: Int) { + + init { + println("$name has ${estimatedGraduationYear - 2020} years left in college.") + } + + // 成员函数 + fun calculateLetterGrade(): String { + return when { + gpa >= 3.0 -> "A" + gpa >= 2.7 -> "B" + gpa >= 1.7 -> "C" + gpa >= 1.0 -> "D" + else -> "E" + } + } +} + +// 创建实例并调用函数时，将执行 when 表达式并返回字母等级 +fun main() { + var student = Student("Lucia", 3.95, "Fall", 2022) + // Prints: Lucia has 2 years left in college. + println("${student.name}'s letter grade is ${student.calculateLetterGrade()}.") + // Prints: Lucia's letter grade is A. +} +``` + + +另见 +--- + +- [Kotlin 语言官方文档](https://kotlinlang.org/) _(kotlinlang.org)_ diff --git a/scripts/assets/kotlin.svg b/scripts/assets/kotlin.svg new file mode 100644 index 0000000..7bc405b --- /dev/null +++ b/scripts/assets/kotlin.svg @@ -0,0 +1,3 @@ + + +