freeCodeCamp/guide/english/kotlin/control-flow/index.md

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Control Flow

Control Flow

Basic Usage

If Expression

if can be used in same way as in other programming languages

var min: Int
if (a < b) {
  min = a
} else {
  min = b
}

else can also be omitted if not needed

if (a < b) {
  print("a is smaller")
}

When Expression

when keyword is replacing usual switch-case expression
The else branch is evaluated if none of the other branch conditions are satisfied
It has powerfull matching branches which support complex evaluations of input argument

when (obj) {
  1          -> "One"
  1, 2       -> "One or Two"
  "Hello"    -> "Greeting"
  is Long    -> "Long"
  !is String -> "Not a string"
  else       -> "Unknown"
}

Range evaluation

when (x) {
  in 1..100 -> print("x is in the range")
  in validNumbers -> print("x is valid")
  !in 10..200 -> print("x is outside the range")
  else -> print("none of the above")
}

For Loops

for loop can iterate through anything that provides and interator, using in operator

val fruits = listOf("apple", "banana", "kiwi")
for (fruit in fruits) {
  println(fruit)
}

Iterating through range of numbers

for (i in 1..5) {
  println(i)
}

While Loops

while and do..while are used like in most programming languages

while (a > 0) {
  a--
}

do {
  val b = provideData()
} while (b != null)

Break and continue keywords

Used like in most other programming languages

Resources

• Basic Syntax Reference
• Kotlin Control Flow Reference