Kotlin is an open-source programming language created by JetBrains that runs on the Java Virtual Machine (JVM) and JavaScript. JetBrains created Kotlin to have a language that cuts down codebase size and is concise while addressing issues in other languages like NullPointerExceptions. The Kotlin language supports features like single-line functions, automatic casting, non-nullable types, and lambda expressions that compile to anonymous classes. Kotlin also supports JavaScript with all language features available in Kotlin code running in Node.js and browsers.

1. Kotlin
L → ∞
@
@selassiabdellah ngMorocco

3. What is Kotlin ?
An open source JVM targeted
language for JVM, Android & JS

4. Why JetBrains do create Kotlin?
IDEs for every language
Language that cut down the codebase
Concise language
Get ride for language issue NPE,..

6. Why JetBrains do create Kotlin?
IDEs for every language
Language that cut down the codebase
Concise language
Get ride for language issues NPE,..

7. The Kotlin Language
Single line function.
Everything is expression in K
Mark return from labels
Lambda compile down to Anonymous
class

8. The Kotlin Language
Auto cast/smart cast
By default vars/types can’t have a null
value
Elvis operator

9. The less side effect you have the more
correct your program is (immutability)
- Hadi Hariri

10. JavaScript support
All language features in Kotlin 1.1
Reflection for JavaScript is not available
Dynamic types (dynamic types to
interoperate with “native” JavaScript
code)

11. JavaScript support
Node.js and the browser Support
npm The Kotlin Standard Library is
available for use through npm)

12. SINGLE LINE FUNCTION
fun double(x: Int): Int = x * 2

13. SINGLE LINE FUNCTION
fun double(x: Int) = x * 2

14. Kotlin By Example @lastIndex
length - 1
lastIndex

15. Kotlin By Example @Nullable
/**
* Consumes the next line of text and returns it.
* Returns null if there are no more lines.
*/
function readUtf8Line() throw "Exception"
/**
* Consumes the next line of text and returns it.
* Returns null if there are no more lines.
*/
fun readUtf8Line(): String?

16. Kotlin By Example @Nothing
fun fail() {
throw RuntimeException("Something went wrong")
}
fun fail(): Nothing {
throw RuntimeException("Something went wrong")
}

17. Kotlin By Example @when
if (firstName.equals("Dad")) {
person.setTeam(programmers);
} else if (lastName.equals("Dihiansan")) {
person.setTeam(designers);
} else {
person.setTeam(others);
}
when {
firstName == "Dan" -> person.team = programmers
lastName == "Dihiansan" -> person.team = designers
else -> person.team = others
}

18. Kotlin By Example @when
switch (firstName) {
case "Dan": person.setTeam(programmers)
break;
case "Jay": person.setTeam(programmers)
break;
case "Jamie": person.setTeam(designers)
break;
default:
person.setTeam(others)
}
when (firstName) {
"Dan", "Jay" -> person.team = programmers
"Jamie" -> person.team = designers
else -> person.team = others
}

19. Kotlin By Example @let
if (message != null) {
System.out.println(message)
}
message?.let { println(it) }

20. Kotlin By Example @?:
if (people == null) {
people = new ArrayList();
}
return people ?: emptyArrayList()

21. if (people == null) {
people = new ArrayList();
}
return people ?: emptyArrayList()

22. Just an ε demo

23. Where do I begin ?
Kotlin.link — almost a complete list of links to
Kotlin projects, libraries and other resources
Kotlin Weekly — a weekly mailing list containing
latest notable news and articles
The Daily Kotlin — Daily Kotlin news and tips

24. QUESTIONS?
@selassiabdellah