Kotlin For Loops & Usage Examples | Android Introduction #14

In this reading, you will learn how to use the for-loop with numbers.

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Let’s review the most important use cases for using for-loops with numbers.

To call code for each number from a to b, including b, use the range a..b inside a for-loop. The following code block should print the numbers 0, 1, 2, 3, 4 and 5.

fun main() {
    val a = 0
    val b = 5
    for (i in a..b) {
        println(i)
    }
}

To call code for each number from a to b, excluding b, use a range a until b inside a for-loop. The following code block should print the numbers 0, 1, 2, 3 and 4.

fun main() {
    val a = 0
    val b = 5
    for (i in a until b) {
        println(i)
    }
}

To call code for each number from a to b, where a is bigger than b, and the step should be -1, use a downTo b inside a for-loop. The below code should print the numbers 5, 4, 3, 2, 1 and 0.

fun main() {
    val a = 5
    val b = 0
    for (i in a downTo b) {
        println(i)
    }
}

To call code for each number from a to b, with a step c, use a..b step c inside a for-loop. The code below should print the numbers 0, 3, 6 and 9.

fun main() {
    val a = 0
    val b = 10
    val c = 3
    for (i in a..b step c) {
        println(i)
    }
}

To call code for each number from a to b, excluding b, with a step c, use a until b step c inside a for-loop. The below code should print the numbers 0, 3 and 6.

fun main() {
    val a = 0
    val b = 9
    val c = 3
    for (i in a until b step c) {
        println(i)
    }
}

To call code for each number from a to b, where a is bigger than b, with a step -c, use a downTo b step c inside a for-loop. The below code should print the numbers 10, 7, 4 and 1.

Note: in kotlin, The step accepts only positive numbers even in case using downTo .

fun main() {
    val a = 10
    val b = 1
    val c = 3
    for (i in a downTo b step c) {
        println(i)
    }
}

You can use this to generate the text for a silly song. Start the code below to find out what it’s going to print.

fun main() {
    for (num in 5 downTo 1) {
        println("$num lemonades are left")
        println("Glupglupglup")
    }
    println("That is it")
    println("Now I have to go")
}

In this reading, you learned how to use the for-loop with numbers.

İbrahim Can Erdoğan

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