Summary - Variables

Combine val, var, const and lateinit to write a profile program.

Summary - Variables

So far you've learned val, var, type inference, const, lateinit and by lazy. val is immutable, var is mutable. The type is usually inferred.

const val is computed at compile-time, lateinit is assigned later, by lazy is computed on first access. Each tool addresses a different deferral need.

Exercise Put it together

At the top level, declare const val MULTIPLIER = 2. Inside fun main(), declare var counter = 5, update with counter = counter * MULTIPLIER, and print with println(counter).

Show example solution

const val MULTIPLIER = 2

fun main() {
    var counter = 5
    counter = counter * MULTIPLIER
    println(counter)
}

Next step

Congratulations! You've completed the variables group. In the next group you'll examine data types in detail: integers (Int, Long), floating-point (Double, Float), Boolean, Char, String and Any/Unit. Each type has a different memory width and use case.

Which type you choose depends on the size and nature of the value. Ready? Let's go.

Test yourself

Which is mutable?
- val
- const val
- by lazy
- var
Show answer

var — A variable declared with var can be reassigned.
Match the concepts

val

Immutable
var

Mutable
const val

Compile-time
lateinit

Assigned later

Summary - Variables: fill in the missing part

var counter = 0
counter ____ 5

Show answer

var counter = 0
counter = 5

Next lesson: Integer types

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