Introduction to Kotlin

Used this slides at GDGMumbai devfest for talking about Kotlin Syntax and also contains steps for how to create a simple backend and frontend with Kotlin. #KotlinEverywhere

Transcript

1. KOTLIN INTRODUCTION TO @msomuin
2. KOTLIN INTRODUCTION TO @msomuin
5. WHY ? HOW ? WHERE ? KOTLIN Intro to
6. WHY ? HOW ? WHERE ? KOTLIN Intro to
7. KOTLIN? What is
8. KOTLIN? What is • Static Language
9. KOTLIN? What is • Static Language • Targeting JVM / Javascript and Native
10. Credits : Jake Wharton
11. Yes! Credits : Jake Wharton
12. What ?? Yes! Credits : Jake Wharton
13. What ?? Who cares ? Yes! Credits : Jake Wharton
14. What ?? Who cares ? Yes! Credits : Jake Wharton
15. What ?? Who cares ? Yes! Credits : Jake Wharton
16. Credits : Jake Wharton
17. Credits : Jake Wharton
18. Credits : Jake Wharton
19. Credits : Jake Wharton
20. Credits : Jake Wharton
21. Credits : Jake Wharton
22. Credits : Jake Wharton
23. Why Kotlin ?
24. OMG, I love JAVA Credits : Kaushik Gopal No Android Developer has ever said
28. #KotlinEverywhere
31. KOTLIN? Where can I use
32. KOTLIN? Where can I use • Anywhere
33. KOTLIN? Where can I use • Anywhere • Android
34. KOTLIN? Where can I use • Anywhere • Android • Similar to Java / Javascript / C# / Groovy allows quick ramp time
35. KOTLIN? Where can I use • Anywhere • Android • Similar to Java / Javascript / C# / Groovy allows quick ramp time • Interoperability allows gradual adoption
36. KOTLIN? How can I use
37. KOTLIN? How can I use • Command Line
38. KOTLIN? How can I use • Command Line • Maven
39. KOTLIN? How can I use • Command Line • Maven • Gradle
40. KOTLIN? How can I use • Command Line • Maven • Gradle • Kobalt
41. KOTLIN? How can I use • Command Line • Maven • Gradle • Kobalt • Ant
42. KOTLIN? How can I use • Command Line • Maven • Gradle • Kobalt • Ant • Intellij Studio
43. KOTLIN? How can I use • Command Line • Maven • Gradle • Kobalt • Ant • Intellij Studio • Android Studio
44. KOTLIN? How can I use • Command Line • Maven • Gradle • Kobalt • Ant • Intellij Studio • Android Studio • Eclipse
45. KOTLIN? How can I use • Command Line • Maven • Gradle • Kobalt • Ant • Intellij Studio • Android Studio • Eclipse • Netbeans
47. public class Main { public static void main(String[] args){ System.out.print("Dabang"); System.out.println("Dabang"); } }
48. fun main(args: Array<String>){ print("Dabang") println("Dabang") }
49. String movieName = “Sholay"; String language = null;
50. val movieName: String = "Sholay" val language: String? = null
51. val movieName: String = "Sholay" val language: String? = null
52. val movieName: String = "Sholay" val language: String? = null
53. val movieName: String = "Sholay" val language: String? = null
54. val firstName: String = "Sholay" val lastName: String? = null
55. val firstName = "Sholay" val lastName: String? = null
56. if (text != null) { int length = text.length(); }
57. text?.let { val length = text.length }
58. val length = text?.length
59. final int andResult = a & b; final int orResult = a | b; final int xorResult = a ^ b; final int rightShift = a >> 2; final int leftShift = a << 2;
60. val andResult = a and b; val orResult = a or b; val xorResult = a xor b; val rightShift = a shr 2; val leftShift = a shl 2;
61. if (score >= 0 && score <= 300) { } // ^^^ Java
62. if (score >= 0 && score <= 300) { } // ^^^ Java vvv Kotlin if (score in 0..300) { }
63. for (int i = 1; i <= 10; i++) { } // ^^^ Java
64. for (int i = 1; i <= 10; i++) { } // ^^^ Java vvv Kotlin for (i in 1..10) { }
65. for (int i = 1; i < 10; i++) { } // ^^^ Java
66. for (int i = 1; i < 10; i++) { } // ^^^ Java vvv Kotlin for (i in 1 until 10) { }
67. for (int i = 10; i >= 0; i--) { } // ^^^ Java
68. for (int i = 10; i >= 0; i--) { } // ^^^ Java vvv Kotlin for (i in 10 downTo 0) { }
69. for (int i = 1; i <= 10; i+=2) { } // ^^^ Java
70. for (int i = 1; i <= 10; i+=2) { } // ^^^ Java vvv Kotlin for (i in 1..10 step 2) { }
71. for (int i = 10; i >= 0; i-=2) { } // ^^^ Java vvv Kotlin for (i in 10 downTo 1 step 2) { }
72. for (String item : collection) { } // ^^^ Java
73. for (String item : collection) { } // ^^^ Java vvv Kotlin for (item in collection) { }
74. for (Map.Entry<String, String> entry: map.entrySet()) {} // ^^^ Java vvv Kotlin for ((key, value) in map) {}
75. for (int number : numbers) { if(number > 5) { System.out.println(number); } }
76. numbers .filter{it > 5} .forEach{ println(it)}
78. class Movie { public String getName() { // .. } public void setName(String name) { // .. } } // ^^^ Java vvv Kotlin val movie = Movie() println("Name is " + movie.name)
79. class Movie { public String getName() { // .. } public void setName(String name) { // .. } } // ^^^ Java vvv Kotlin val movie = Movie() println("Name is " + movie.name)
80. class Movie { public String getName() { // .. } public void setName(String name) { // .. } } // ^^^ Java vvv Kotlin val movie = Movie() println("Name is " + movie.name)
81. class Movie { public String getName() { // .. } public void setName(String name) { // .. } } // ^^^ Java vvv Kotlin val movie = Movie() println("Name is ${movie.name})
82. class Movie { public String getName() { // .. } public void setName(String name) { // .. } } // ^^^ Java vvv Kotlin val movie = Movie() println("Name is $movie)
83. class Movie { var name = "Sholay" } // ^^^ Kotlin vvv Java Movie movie = new Movie(); System.out.println("Name is " + movie.getName()); movie.setName("Kabali");
84. class Movie { var name = "Sholay" } // ^^^ Kotlin vvv Java Movie movie = new Movie(); System.out.println("Name is " + movie.getName()); movie.setName("Kabali");
85. class Movie { var name = "Sholay" } // ^^^ Kotlin vvv Java Movie movie = new Movie(); System.out.println("Name is " + movie.getName()); movie.setName("Kabali");
86. class Movie { var name = "Sholay" } // ^^^ Kotlin vvv Java Movie movie = new Movie(); System.out.println("Name is " + movie.getName()); movie.setName("Dabang");
87. val movie = Movie() movie = Movie() var currentMovie = Movie() currentMovie = Movie()
88. val movie = Movie() movie = Movie() var currentMovie = Movie() currentMovie = Movie()
89. val movie = Movie() movie = Movie() var currentMovie = Movie() currentMovie = Movie()
90. fun Date.isReleaseDay(): Boolean { return day == 5 }
91. fun Date.isReleaseDay(): Boolean { return day == 5 } val today = Date() if(today.isReleaseDay()){ println("Today is a release day") }else{ println("Today is not a release day") }
92. fun Date.isReleaseDay(): Boolean { return day == 5 } val today = Date() if(today.isReleaseDay()){ println("Today is a release day") }else{ println("Today is not a release day") }
93. fun Date.isReleaseDay(): Boolean { return day == 5 } val today = Date() if(today.isReleaseDay()){ println("Today is a release day") }else{ println("Today is not a release day") } // ^^^ Kotlin vvv Java DateKt.isReleaseDay(today)
94. class Movie{ val name = "Dabang" }
95. class Movie(name : String){ val name = name }
96. class Movie(val name: String){ }
97. class Movie(val name: String)
98. class Movie(val name: String) val movie = Movie(“Dabang“) println("Hello, $movie!")
99. class Movie(val name: String) val movie = Movie("Dabang") println("Hello, $movie!”) Hello, Movie@78308db1!
100. data class Movie(val name: String) val movie = Movie("Dabbing") println("Hello, $movie!”) Hello, Movie@78308db1!
101. data class Movie(val name: String) val movie = Movie("Dabang") println("Hello, $movie!”) Hello, Movie(name=Dabang)!
102. data class Movie(val name: String)
103. public class Movie { private String name; public Movie(String name) { this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return “Movie{name=" + name”}”; } }
104. data class Money(val amount: Int, val currency:String)
105. data class Money(val amount: Int, val currency:String) val ticket = Money(120,"₹")
106. data class Money(val amount: Int, val currency:String) val ticket = Money(amount = 120, currency = "₹")
107. data class Money(val amount: Int, val currency:String) val ticket = Money(currency = "₹",amount = 120)
108. data class Money(val amount: Int, val currency:String ="₹") val ticket = Money(currency = "₹",amount = 120)
109. data class Money(val amount: Int, val currency:String ="₹") val ticket = Money(amount = 120)
110. val ticket = Money(amount = 120) val popcorn = Money(amount = 85) val coke = Money(amount = 45)
111. val ticket = Money(amount = 120) val popcorn = Money(amount = 85) val coke = Money(amount = 45) private val Int.m: Money get() { return Money(this, “₹") }
112. val ticket = 120.m val popcorn = 85.m val coke = 45.m private val Int.m: Money get() { return Money(this, “₹") }
113. val ticket = 120.m val popcorn = 85.m val coke = 45.m val total = // ??
114. val ticket = 120.m val popcorn = 85.m val coke = 45.m val total = // ?? fun Money.plus(other: Money): Money { if (currency != other.currency) { throw IllegalArgumentException("Currency Mismatch") } return copy(amount = amount + other.amount) }
115. val ticket = 120.m val popcorn = 85.m val coke = 45.m val total = ticket.plus(popcorn).plus.(coke) fun Money.plus(other: Money): Money { if (currency != other.currency) { throw IllegalArgumentException("Currency Mismatch") } return copy(amount = amount + other.amount) }
116. val ticket = 120.m val popcorn = 85.m val coke = 45.m val total = ticket + popcorn + coke fun Money.plus(other: Money): Money { if (currency != other.currency) { throw IllegalArgumentException("Currency Mismatch") } return copy(amount = amount + other.amount) }
117. val ticket = 120.m val popcorn = 85.m val coke = 45.m val total = ticket + popcorn + coke operator fun Money.plus(other: Money): Money { if (currency != other.currency) { throw IllegalArgumentException("Currency Mismatch") } return copy(amount = amount + other.amount) }
118. fun convertToRupee(money: Money) : Money { when (money.currency) { "₹" -> return money "$" -> return Money(money.amount / 65, "₹") else -> throw // .. } }
119. fun convertToRupee(money: Money) : Money { when (money.currency) { "₹" -> return money "$" -> return Money(money.amount / 65, "₹") else -> throw // .. } }
120. fun convertToRupee(money: Money) : Money { return when (money.currency) { "₹" -> money "$" -> Money(money.amount / 65, "₹") else -> throw // .. } }
121. fun convertToRupee(money: Money) = when (money.currency) { "₹" -> money "$" -> Money(money.amount / 65, "₹") else -> throw // .. }
122. fun Int.percentOf(money: Money) : Int{ return money.amount * this / 100 }
123. fun Int.percentOf(money: Money) = money.amount * this / 100
124. fun Int.percentOf(money: Money) = money.amount * this / 100 val ticket = Money(120, "₹") 28.percentOf(ticket)
125. fun Int.percentOf(money: Money) = money.amount * this / 100 val ticket = Money(120, "₹") 28 percentOf ticket
126. infix fun Int.percentOf(money: Money) = money.amount * this / 100 val ticket = Money(120, "₹") 28 percentOf ticket
128. Button confirm = (Button) findViewById(R.id.confirm); confirm.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Log.d(TAG,"Confirm Clicked!"); } });
129. val confirm = findViewById<Button>(R.id.confirm); confirm.setOnClickListener({ view -> Log.d(TAG,”Confirm Clicked!") })
130. val confirm = findViewById<Button>(R.id.confirm); confirm.setOnClickListener(){ Log.d(TAG,”Confirm Clicked!") }
131. val confirm = findViewById<Button>(R.id.confirm); confirm.setOnClickListener{ Log.d(TAG,”Confirm Clicked!") }
132. val confirm = findViewById(R.id.confirm); confirm.setOnClickListener{ Log.d(TAG,”Confirm Clicked!") }
133. confirm.setOnClickListener{ Log.d(TAG,”Confirm Clicked!") }
134. fun getAllMovies() = arrayListOf( Movie(2016, "Kabali"), Movie(2015, "Bahubali 1"), Movie(2017, "Bahubali 2"), Movie(2018, "2.0"), Movie(2017, “Dangal"), //... )
135. fun getAllMovies() = arrayListOf( Movie(2016, "Kabali"), Movie(2015, "Bahubali 1"), Movie(2017, "Bahubali 2"), Movie(2018, "2.0"), Movie(2017, “Dangal"), //… ) val movies = getAllMovies() val movie17 = movies.filter { it.year == 2017 }
136. fun getAllMovies() = arrayListOf( Movie(2016, "Kabali"), Movie(2015, "Bahubali 1"), Movie(2017, "Bahubali 2"), Movie(2018, "2.0"), Movie(2017, “Dangal"), //… ) val movies = getAllMovies() val movie17 = movies.filter { it.year == 2017 }
137. val movie17 = movies.filter { it.year == 2017 } .sortedBy { it.name }
138. Kotlin Lib
139. Kotlin Lib • sortedBy
140. Kotlin Lib • sortedBy • containsAll
141. Kotlin Lib • sortedBy • containsAll • indexOf
142. Kotlin Lib • sortedBy • containsAll • indexOf • lastIndexOf
143. Kotlin Lib • sortedBy • containsAll • indexOf • lastIndexOf • subList
144. val tickets = Money(120, "INR") val popcorn = tickets.copy()
145. val tickets = Money(120, "INR") val popcorn = tickets.copy() if (tickets == popcorn) { println("They are same in values”) }
146. val tickets = Money(120, "INR") val popcorn = tickets.copy() if (tickets == popcorn) { println("They are same in values”) } if (tickets !== popcorn) { println("They are different in address”) }
150. Key Features
151. Key Features • null safety
152. Key Features • null safety • not checked exceptions
153. Key Features • null safety • not checked exceptions • getters & setters
154. Key Features • null safety • not checked exceptions • getters & setters • delegations
155. Key Features • null safety • not checked exceptions • getters & setters • delegations • lateinit
156. Key Features • null safety • not checked exceptions • getters & setters • delegations • lateinit • named & optional arguments
157. Key Features • null safety • not checked exceptions • getters & setters • delegations • lateinit • named & optional arguments • lambdas
158. Key Features • null safety • not checked exceptions • getters & setters • delegations • lateinit • named & optional arguments • lambdas • extension functions
159. Key Features • null safety • not checked exceptions • getters & setters • delegations • lateinit • named & optional arguments • lambdas • extension functions • type aliases
160. Java
 Interop Java and Kotlin in one place
161. Kotlin
162. Lets move to web ?
163. Lets move to web ? • Yes this slide is correct, and of-course you are sitting on the mobile track session only.
164. Lets move to web ? • Yes this slide is correct, and of-course you are sitting on the mobile track session only. • Why should only Web developers have all fun.
 ( React-Native eh ? #KotlinEverywhere )
165. Lets move to web ? • Yes this slide is correct, and of-course you are sitting on the mobile track session only. • Why should only Web developers have all fun.
 ( React-Native eh ? #KotlinEverywhere ) • Lets quickly do some web things
166. We will use #KotlinEverywhere
167. We will use #KotlinEverywhere • Backend
168. We will use #KotlinEverywhere • Backend • Frontend
169. We will use #KotlinEverywhere • Backend • Frontend • Of-course Apps
170. Create New Project
175. Create Backend Module
180. Create Frontend Module
187. fun main(args: Array<String>) { embeddedServer(Netty, 8080) { routing { get("/api/ping/{count?}") { var count = Integer.valueOf(call.parameters["count"]?: "1") if (count < 1) { count = 1 } var obj = Array<Entry>(count, {i -> Entry("$i: Hello, World!")}) var gson = Gson() gson = Gson() var str = gson.toJson(obj) call.response.header("Access-Control-Allow-Origin", "*") call.respondText(str, ContentType.Application.Json) } } }.start(wait = true) } data class Entry(val message: String)
191. <!DOCTYPE html> <!-- index.html --> <html lang="en"> <head> <meta charset="UTF-8"> <title>Console Output</title> </head> <body> <div style="display:block"> <label for="count_id">Enter number of elements to fetch:</label> <input id="count_id" name="count" value="1"/> </div> <button id="button_id" type="button" style="display:block">Submit</button> <textarea id="textarea_id" style="width: 100%; height: 200px"> </textarea> <script type="text/javascript" src="js/lib/kotlin.js"></script> <script type="text/javascript" src="js/app.js"></script> </body> </html>
192. fun main(args: Array<String>) { window.onload = { fetch("1") val head = document.getElementsByTagName("head") head[0]?.appendChild(createStylesheetLink("style.css")) val input = document.getElementById("count_id") as HTMLInputElement val button = document.getElementById("button_id") button?.addEventListener("click", fun(event: Event) { fetch(input.value) }) } }
193. fun fetch(count: String): Unit { val url = "http://localhost:8080/api/ping/$count" val req = XMLHttpRequest() req.onloadend = fun(event: Event){ val text = req.responseText println(text) val objArray = JSON.parse<Array<Json>>(text) val textarea = document.getElementById("textarea_id") as HTMLTextAreaElement textarea.value = "" objArray.forEach { val message = it["message"] textarea.value += "$message\n" } } req.open("GET", url, true) req.send() }
194. fun createStylesheetLink(filePath: String): Element { val style = document.createElement("link") style.setAttribute("rel", "stylesheet") style.setAttribute("href", filePath) return style }
201. How long will it take to move from Java to Kotlin?
202. Credits : Maria Neumayer
203. Disclaimer : It may take more than 22 hours Credits : Maria Neumayer
205. https://try.kotlinlang.org/
206. Plugin
212. Copy Java -> Paste in Kotlin
213. Awesome.
216. With #Kotlin develop apps for the next billion people
220. Any Questions? @msomuin Inspiration • Hadi Hariri • Jake Wharton