Kotlin For Loop

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) {
        val marks = arrayOf(80,85,60,90,70)
        for(item in marks){    
            println(item)
        }
     }

Output:
80
85
60
90
70

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) {
    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) {
    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) {
    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

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