Mobile Development

Kotlin Basics

Essential Kotlin syntax: variables, null safety, functions.

Variables

# Mutable
var age = 25
var name = "John"
age = 26

# Immutable
val pi = 3.14
val app = "MyApp"

Null Safety

# Non-nullable
var name: String = "John"

# Nullable
var name: String? = null

# Safe call
val length = name?.length

# Elvis operator
val len = name?.length ?: 0

Functions

# Basic
fun greet() {
    println("Hello")
}

# With return
fun add(a: Int, b: Int): Int {
    return a + b
}

# Single expression
fun add(a: Int, b: Int) = a + b

When Expression

when (day) {
    1 -> println("Monday")
    2 -> println("Tuesday")
    else -> println("Other")
}

# Range
when (score) {
    in 90..100 -> "A"
    in 80..89 -> "B"
    else -> "C"
}