The for loop iterates through a collection, more specifically through anything that provides an iterator.

for (item in collection)
{
    //Code to perform
}

Syntax to use for loop in Kotlin.

In Kotlin, you can use for loop to iterate through following things

• • • Range
    • Array
    • String
    • Collection

var myRange = 1..10
for (x in myRange )
{
    println(x)
}

Example

The program will print numbers 1 through 10. During each step of the loop, the variable x will contain the value of the current element in the range.

Iterate through a String using For Loop

Without using index property

fun main(args: Array) 
{
    var name = "inspire_coding" 
    for (letter in name)
    {
        println(letter)
    }
}

i
n
s
p
i
r
e
_
c
o
d
i
n
g

Iterate String Using Index property

fun main(args: Array) 
{
    var name = "inspire_coding" 
    for (index in name.indices)
    {
        println(name[index])
    }
}

i
n
s
p
i
r
e
_
c
o
d
i
n
g

Iterate String Using withIndex() Library Function

fun main(args: Array) 
{
    var name = "inspire_coding" 
    for ((index , value) in name.withIndex())
    {
        println("$index" + "th position: $value")
    }
}

0th position: i
1th position: n
2th position: s
3th position: p
4th position: i
5th position: r
6th position: e
7th position: _
8th position: c
9th position: o
10th position: d
11th position: i
12th position: n
13th position: g

Different ways to iterate through Range

Here, we have range from 1 to 6 which is being traversed from first to last item using for loop in kotlin.

fun main(args: Array) 
{ 
    for (i in 1..6)
    {
        println(i)
    }
}

1
2
3
4
5
6

Here, we have range from 1 to 6. But, we are iterating the Range in reverse order i.e. from last item to first item.

fun main(args: Array) 
{ 
    for (i in 6.downTo(1))
    {
        println(i)
    }
}

6
5
4
3
2
1

Here, we have range from 1 to 6. We are iterating the Range from first item to last item in steps of 2.

fun main(args: Array) 
{ 
    for (i in 1..6 step 2)
    {
        println(i)
    }
}

1
3
5

Here, we have range from 1 to 6. But, we are iterating the Range in reverse order i.e. from last item to first item. Also, we are iterating in steps of 2.

fun main(args: Array) 
{ 
    for (i in 6 downTo 1 step 2)
    {
        println(i)
    }
}

6
4
2

Questions

I hope the description was understandable and clear. But if you have still questions, then leave me comments below! 😉

Have a nice a day! 🙂

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