Kotlin for Beginners — #1: “for” loop
Kotlin ‘for’ loop in 2 min (Updated — Jun, 2020)
All you need to know about ‘for’ loop in Kotlin
for
loop iterates over anything that is iterable (anything that has aniterator()
function that provides anIterator
object), or anything that is itself anIterator
.— Kotlin Doucmentation
in
— Simplest for loop which iterates over every element of the list
val fruits = listOf("Apple", "Banana", "Cherries", "Guava")
for (fruit in fruits) {
println(fruit)
}// Prints: Apple, Banana, Cherries, Guava
2. ..
— Iterate over a range between 0 (included) to 5 (included)
for (number in 0..5) {
println(number)
}// Prints: 0 through 5
3. until
— For range between 0 (included) to 5 (excluded)
for (number in 0 until 5) {
println(number)
}// Prints: 0 through 4
4. downTo
— Iterate decreasingly from 5 (included) to 0(included)
for (number in 5 downTo 0) {
println(number)
}// Prints: 5 to 0
5. step
— Jump while iterating over numbers
for (number in 0..10 step 2) {
println(number)
}
// Prints: 0, 2, 4, 6, 8, 10
for (number in 10 downTo 0 step 2) {
println(number)
}
// Prints: 10, 8, 6, 4, 2, 0val fruits = listOf("Apple", "Banana", "Cherries", "Guava")
for (index in fruits.indices step 2) {
println(fruits[index])
}
// Prints: Apple, Cherries
6. withIndex()
— Iterate over the list with an index of the current item.
val fruits = listOf("Apple", "Banana", "Cherries", "Guava")
for ((index, fruit) in fruits.withIndex()) {
println("$index - $fruit")
}// Prints: 0 - Apple, 1 - Banana, 2 - Cherries, 3 - Guava
7. indices
— Iterate a list through indexes
val fruits = listOf("Apple", "Banana", "Cherries", "Guava")
for (index in fruits.indices) {
println(fruits[index])
}// Prints: Apple, Banana, Cherries, Guava
8. Iterate over Map using entries as objects
val fruitMap = mapOf("A" to "Apple",
"B" to "Banana",
"C" to "Cherries",
"G" to "Guava")
for (entry in fruitMap) {
println(entry.key + "-" + entry.value)
}
// Prints: A-Apple, B-Banana, C-Cherries, G-Guava
for ((key, value) in fruitMap) {
println(key + "-" + value)
}
// Prints: A-Apple, B-Banana, C-Cherries, G-Guava
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