📌 For Loop in Kotlin

The for loop in Kotlin is used to iterate over a range, collection, array, or any iterable object. It provides a clean and concise syntax for traversing data.

✅ 1. Syntax of For Loop

kotlin
for (i in 1..5) {    println("Number: $i")}

Output:

javascript
Number: 2Number: 3Number: 4Number: 5

• 1..5 includes both 1 and 5.

📌 Example 2: Using until (Exclusive Range)

kotlin
for (i in 1 until 5) {    println("Number: $i")}

Output:

javascript
Number: 2Number: 3Number: 4

• until excludes the last value (5).

✅ 3. For Loop with Step

You can specify a step using the step keyword to skip numbers.

📌 Example:

kotlin
for (i in 1..10 step 2) {    println("Step: $i")}

Output:

makefile
Step: 3Step: 5Step: 7Step: 9

• step 2 increments by 2 each time.

✅ 4. For Loop in Reverse

You can iterate in reverse using the downTo keyword.

📌 Example:

kotlin
for (i in 10 downTo 1) {    println("Countdown: $i")}

Output:

makefile
Countdown: 9Countdown: 8Countdown: 7Countdown: 6Countdown: 5Countdown: 4Countdown: 3Countdown: 2Countdown: 1

• downTo iterates in decreasing order.

✅ 5. For Loop with Arrays and Collections

You can iterate over arrays, lists, sets, or maps using for.

📌 Example: Iterate Over an Array

kotlin
val fruits = arrayOf("Apple", "Banana", "Cherry")for (fruit in fruits) {    println(fruit)}

Output:

nginx
AppleBananaCherry

📌 Example: Iterate Over a List with Index

You can use withIndex() to get both index and value.

kotlival colors = listOf("Red", "Green", "Blue")
for ((index, color) in colors.withIndex()) {    println("Index: $index, Color: Index: 0, Color: RedIndex: 1, Color: GreenIndex: 2, Color: Blue

📌 Example: Iterate Over a Map

kotlin
val users = mapOf("Alice" to 25, "Bob" to 30)for ((name, age) in users) {    println("$name is $age years old")}

Output:

pgsql
Alice is 25 years oldBob is 30 years old

✅ 6. Conclusion

• Use .. for inclusive ranges.

• Use until for exclusive ranges.

• Use step to increment values.

• Use downTo to iterate in reverse.

• Use withIndex() for index-value iteration.

• Use destructuring for maps using (key, value).