Kotlin for Loop

Kotlin for loop is used to iterate a part of program several times. It iterates through arrays, ranges, collections, or anything that provides for iterate. Kotlin for loop is equivalent to the foreach loop in languages like C#.

Syntax of for loop in Kotlin:

for (item in collection){
//body of loop
}

Iterate through array

Let's see a simple example of iterating the elements of array.

fun main(args : Array<String>) {
    val marks = arrayOf(80,85,60,90,70)
    for(item in marks){
        println(item)
    }
}

Output:

If the body of for loop contains only one single line of statement, it is not necessary to enclose within curly braces {}.

fun main(args : Array<String>) {
    val marks = arrayOf(80,85,60,90,70)
    for(item in marks)
        println(item)
}

The elements of an array are iterated on the basis of indices (index) of array. For example:

fun main(args : Array<String>) {
   
    val marks = arrayOf(80,85,60,90,70)
    for(item in marks.indices)
       println("marks[$item]: "+ marks[item])
}

Output:

marks[0]: 80
marks[1]: 85
marks[2]: 60
marks[3]: 90
marks[4]: 70

Iterate through range

Let's see an example of iterating the elements of range.

fun main(args : Array<String>) {

    print("for (i in 1..5) print(i) = ")
    for (i in 1..5) print(i)
    println()
    print("for (i in 5..1) print(i) = ")
    for (i in 5..1) print(i)             // prints nothing
    println()
    print("for (i in 5 downTo 1) print(i) = ")
    for (i in 5 downTo 1) print(i)
    println()
    print("for (i in 5 downTo 2) print(i) = ")
    for (i in 5 downTo 2) print(i)
    println()
    print("for (i in 1..5 step 2) print(i) = ")
    for (i in 1..5 step 2) print(i)
    println()
    print("for (i in 5 downTo 1 step 2) print(i) = ")
    for (i in 5 downTo 1 step 2) print(i)
}

Output:

for (i in 1..5) print(i) = 12345
for (i in 5..1) print(i) = 
for (i in 5 downTo 1) print(i) = 54321
for (i in 5 downTo 2) print(i) = 5432
for (i in 1..5 step 2) print(i) = 135
for (i in 5 downTo 1 step 2) print(i) = 531

Next TopicKotlin while Loop

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