An introduction to writing Kotlin

Lesson 1 · On the house

Hello, Kotlin

fun main, println, top-level entry.

Lesson 2

val and var

Prefer val; inference; reassignment rules.

Lesson 3

Types you can see

Int, Double, String, Boolean; annotations.

Lesson 4

String templates

$name, ${expr}, and raw strings.

Lesson 5

if and when

if as expression; when branches; Boolean conditions.

Lesson 6

Loops

for ranges, until, while, break/continue.

Lesson 7

Functions

fun, params, return types, single-expression =.

Lesson 8

Null safety

String?, ?., ?:, !!, and smart casts.

Lesson 9

Collections

listOf, mutableListOf, mapOf, indexing, size.

Lesson 10

Data classes

data class, copy, destructuring; a tiny program.