Kotlin Tour

Variables

https://kotlinlang.org/docs/reference/basic-syntax.html#defining-local-variables

Read-only variables

Kotlin let you declare variables as immutable by using the val keyword :

val a: Int = 42 // Type is declared after name
val b = 5       // Int is inferred
val c: Int      // Initialization is deferred so we need to specify type
c = 3

Warning : As in Java (final) or JavaScript (const), val makes only the reference be immutable, not the object being referenced itself :

val languages = mutableListOf("Java", "JavaScript")
languages.add("Kotlin") // [Java, JavaScript, Kotlin]

Mutable variables

Using the var keyword you can declare a mutable variable =

var d = 41
d += 1     // What is the answer ?

Exercice

Constants

You can also declare compile-time constants with the const keyword :

const val CONST = 42

Only usable for top-level or object member and String "primitive" types

Strings

Type

https://kotlinlang.org/docs/reference/basic-types.html#strings

As in Java String are immutables. They are also iterables.

Kotlin has two types of strings :

1. Literals, using "
2. Raw, using """

Raw strings can contain newlines and other characters :

Tell me and I forget.
Teach me and I remember.
Involve me and I learn.
(Benjamin Franklin)

Templates

https://kotlinlang.org/docs/reference/basic-types.html#string-templates

Using $ or ${...} in a string allows you to reference variables and call functions.