This document provides an introduction and overview of the Kotlin programming language from the perspective of an Android engineering manager. It discusses that Kotlin is a programming language that runs on the JVM and was created by JetBrains as an alternative to Java for Android development. The document then covers various Kotlin concepts and features such as syntax, OOP concepts, properties, loops, lambdas, extensions and more in a conversational FAQ format. It also provides some useful Kotlin resources for learning more.

2. Who am I?
 Corneliu Balaban
 Mobile Engineering Manager @ Avira Romania
 Android aficionado with BI background
 Catching up on the “Kotlin for iOS” – Swift
 Passionate about BioMedical and AgriTech

3. What is this …
Kotlin?
 It is a Russian Island close
to St. Petersburg
 Initially belong to Sweden
but after Russia annexed it
and …
 Inspired the name for a new
programming language
running in the JVM
 Created by JetBrains,
creators of PhpStorm,
WebStorm, PyCharm etc
 Ads small overhead to the
Android dev env and dex
method count increase by
~6k methods

4. What have we
been missing
inJava?
 No need for functional interfaces in order to implement own
higher functions and lambda’s
 Embedded lists iterators and mapping functions
 Class extensions (well… Swift has them)
 Strongly typed with inferred data types
 No elegant ways of avoiding NPE’s

5. Basic Kotlin
syntax
fun sayHello(name: String): Unit {
print("Hello ${name}!" + "Welcome to Bucharest Mobile Meetup");
}
OR
fun sayHello(name: String): Unit = print("Hello ${name}!" + "Welcome to Bucharest
Mobile Meetup");
OR
fun sayHello(name: String) = print("Hello ${name}!" + "Welcome to Bucharest
Mobile Meetup");

6. OOP concepts
Kotlin classes
 Inherit from Java’s equivalent of Object  Any
 By default are final
 Inheritance is enabled by prefixing the class with "open"
 Primary constructor is embedded in the class signature . It cannot
contain any code
 Secondary constructors are available. Need to delegate to primary
constructor
 init() methods come to the rescue
 Immutable variables are represented by the prefix "val" and can have
inferred data type

7. OOP concepts
Good ol' "bean"
 Easily accessible via "data classes"
 Makes a good separation of code if you want some objects that just
need to hold data
 Can make use of companion objects to hold “static” values

8. MoreOOP …
 Java developers love to be "static"
 Bad luck, there are no class level methods
 "Companion objects" are the new black
 Used to replicate "statics" behavior in Kotlin
 Can be one per class
 Static variables are not available other than via " companion
objects

9. var, val … do I
need to know
them?
 Immutable objects/ variables are prefixed with "val"
 Can be initialized at declaration time. No data type needed as
inference works as a charm
 If they cannot be initialized at declaration time then data type is
mandatory
 Are there other kinds of immutable objects?
 var toDoList1: List<ToDoModel> = listOf(ToDoModel(name="Buy
Milk"),ToDoModel(name="Buy Weed"));
• var toDoList: MutableList<ToDoModel> = mutableListOf()

10. If val reffers to
immutable, do
I have project
level constants
 Compile time constants are defined using
the prefix "const”
 Cannot have a custom getter
 Can be used in annotations
 Can only be of type String or another
primitive
 Can or cannot be part of a class/ object
 Immutable and mutable properties have intrinsic get and set methods
 You can customize the visibility of the setter and or getter as well as their
behavior
 Since properties need to be assigned values at compile time, the only
way to define properties that can receive runtime values is by using the
prefix "lateinit"

11. Optionals &
null safe
accessors
 Swift has them so why not Kotlin as well
 They are some weird implementation of Schroedingers cat
 Optional properties can contain a value or can be null
 Methods can return optionals as well
• To access potentially null variables/ objects you
can use ?.
• In chaining if at least one of the conditions
is null then the entire chained expression is
null

12. Loops,
operator
overloading
and string
interpolation
 Iterating collections is easier with " for – in " loops . No more of the
Java " for – each" nightmare
 Range loops are introduces to help us run code for exact number
of times " for i in 1 .. 27"
 Operator overloading has been made available yet by another
language running on top on the JVM ( as did Groovy)
 String templates and interpolations are yet another valuable

13. Lambdas and
higher order
functions
 Introduced in Java 8 but cumbersome to use.Why?
 Cumbersome to introduce as functional interfaces are needed
 Not backwards compatible
 Not really useful for Android developers as we are still stuck on Java
7
 Lambdas are natively supported by Kotlin
 Kotlin allows methods that can receive other functions as
parameters
 Also it allows the existence of functions outside classes which is
perfect for utils

14. Extensions
 Imagine that "String" would have an … ”getGreetingById" method
 Extensions can be used to add custom methods to existing objects
 They can be called as : Object. getGreetingById(1)
 Very similar to Swift extensions

15. Useful
resources
 Must try the "anko" library: https://github.com/Kotlin/anko
 Get dirty with Kotlin Koans here:
http://try.kotlinlang.org/#/Kotlin%20Koans/Introduction/Strings/T
ask.kt
 Try reading Antonio Leiva's Kotlin book:
https://leanpub.com/kotlin-for-android-developers

16. Oh, and one
more thing …
adding Kotlin
to your project
 Not going through all the steps ;)
 Check them here:
https://blog.jetbrains.com/kotlin/2013/08/working-with-kotlin-in-
android-studio/

17. Q &A