Loops
Loops
Video Explanation
for Loop
The for loop is used to iterate over ranges, arrays, or collections.
Iterating over a Range
fun main() {
for (i in 1..5) {
println(i)
}
// Output: 1 2 3 4 5
}
Descending Range with downTo
fun main() {
for (i in 5 downTo 1) {
println(i)
}
// Output: 5 4 3 2 1
}
Step Increment with step
fun main() {
for (i in 0..20 step 5) {
println(i)
}
// Output: 0 5 10 15 20
}
Exclusive Range with until
fun main() {
for (i in 1 until 5) {
println(i)
}
// Output: 1 2 3 4 (excludes 5)
}
Iterating over an Array
fun main() {
val fruits = arrayOf("Apple", "Banana", "Cherry")
for (fruit in fruits) {
println(fruit)
}
}
Iterating with Index
fun main() {
val colors = arrayOf("Red", "Green", "Blue")
for ((index, color) in colors.withIndex()) {
println("$index: $color")
}
}
while Loop
Repeats as long as the condition is true.
fun main() {
var count = 1
while (count <= 5) {
println("Count: $count")
count++
}
}
do-while Loop
Executes the block at least once, then checks the condition.
fun main() {
var num = 1
do {
println("Number: $num")
num++
} while (num <= 5)
}
break — Exit a Loop
fun main() {
for (i in 1..10) {
if (i == 6) break
println(i)
}
// Output: 1 2 3 4 5
}
continue — Skip an Iteration
fun main() {
for (i in 1..10) {
if (i % 2 == 0) continue
println(i)
}
// Output: 1 3 5 7 9 (odd numbers only)
}
Labeled Loops
Labels help break or continue outer loops:
fun main() {
outer@ for (i in 1..3) {
for (j in 1..3) {
if (j == 2) continue@outer
println("i=$i, j=$j")
}
}
}
Output:
i=1, j=1
i=2, j=1
i=3, j=1
Nested Loops — Multiplication Table
fun main() {
for (i in 1..5) {
for (j in 1..5) {
print("${i * j}\t")
}
println()
}
}
repeat() Function
fun main() {
repeat(5) { index ->
println("Iteration $index")
}
}
Iterating Over a String
fun main() {
val word = "Kotlin"
for (char in word) {
print("$char ")
}
// Output: K o t l i n
}
Loop Summary
| Loop Type | When to Use |
|---|---|
for | Known number of iterations or iterating a collection |
while | Repeat while condition is true (check first) |
do-while | Execute at least once (check after) |
repeat(n) | Run exactly n times with index available |
break | Exit loop early |
continue | Skip current iteration |
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