Intro to Kotlin

At the latest Google I/O conference, Google announced that Android development would now fully support Kotlin. This is big news as it opens up an entirely new avenue for those that want to start creating their own Android applications. And seeing as Kotlin is highly popular and has a lot of unique features, it creates new opportunities for existing developers too.

Kotlin is a statically typed programming language from JetBrains. It is fully ‘inter-operable’ with Java (meaning you can use Java frameworks and even mix commands from both in your code) and comes with no limitations. Android developers have actually been using Kotlin for some time already via a plugin and some popular apps on the Play Store (like Basecamp) were reportedly built solely using Kotlin. Now though, as of the forthcoming Android Studio 3.0, it will be bundled-in and supported out-of-the-box.

Transcript

1. Introduction to Kotlin Livin Mathew Android Lead LmntrX Tech
2. Kotlin
3. Why Kotlin?
4. Some Java issues addressed in Kotlin - Null references are addressed by type system - No raw type - Invariant Arrays - Proper function types - Use-site variance - No checked exceptions
5. What Java has that Kotlin does not? - Checked Exceptions - Primitive Types - Static Members - Non-private fields - Wildcard-types - NullPointerException
7. What Kotlin has that Java does not? A ton of things...
8. Mutable and Immutable objects val pi = 3.14 var rad = 5 var hello: String = “Hello World” val key: String = “GDG Cochin”
9. Null Safety var a = null var hello: String = null var hello: String? = null var hello: String lateinit var hello: String
10. Ranges val a = 1..4 val a = 4..1 val a = 4 downto 1 val a = 1 until 4 val a = 1..10 step 2
11. Strings Templates val i = 8 val s = “i = $i” val str = abc print(“Length of $str is ${str.length}”) Length of abc is 3 i = 8
12. Conditional Constructs if(a > b){ s = “larger” } else { s = “smaller” } val s = if(a > b) “Larger” else “Smaller”
13. val s = if(a > b){ print(“a is largest”) “Larger” } else { print(“b is largest”) “Smaller” }
14. val s = when(someChar){ ‘A’ -> “Hello” ‘a’ -> “World” else -> “Invalid Char” }
15. Looping Constructs for( object in objects ) print(object.name) while( a > b ){ a = a + c } do{ val y = doSomething() }while( y != null )
16. Class - Final class - Open class - Object class - Data class class Dog{ var breed; }
17. Properties - Mutable - var - Immutable - val
18. Functions fun sm(i: Int, j: Int): Int{ return if (i>j) j else i } sm(5,2) => 2
19. Single Expression Function fun sm(i: Int, j: Int ): Int = if (i>j) j else i sm(5,2) => 2
20. Extension Functions fun Int.sm(j: Int): Int = if (this>j) j else this 5.sm(2) => 2
22. Infix Notation infix fun Int.sm(n: Int): Int = if (this>n) n else this 5 sm 2 => 2
23. Constructors - Primary class Dog(var breed:String, var age:Int) - Secondary class Dog{ constructor(var breed:String, var age:Int){} }
24. Package Level Stuff package foo.bar fun baz(){} val boo = 2 class Goo{}
26. Higher Order Functions - Function as parameter - Or returns a function
27. Lambda - Function Literal - Function that is not declared but passed immediately as an expression
28. https://github.com/Livin21 /BookStoreKotlinSkeleton
29. Questions
30. Livin Mathew Android Lead LmntrX Tech livin@livinmathew.me /livin21 /livin_mathew /@livinmathew