Introduction
Control flow is essential in programming, allowing you to dictate the execution order of your code. In Kotlin, you can use conditionals to make decisions and loops to repeat actions.
In this post, we’ll cover:
✅ Conditional Statements: if, else, when
✅ Loops: for, while, and do-while
✅ Best Practices for Using Control Flow
By the end of this post, you’ll know how to control the flow of your Kotlin programs using these powerful tools!
1. Conditional Statements
Conditional statements help you execute code based on certain conditions. In Kotlin, you can use if, else, and when.
✅ if and else
The if statement evaluates a condition, and if it’s true, the block of code inside it is executed. You can use else to provide an alternative if the condition is false.
val age = 18
if (age >= 18) {
println("You are an adult")
} else {
println("You are a minor")
}
✅ if as an Expression
In Kotlin, if can also be used as an expression, meaning it can return a value. This is different from languages like Java, where if is a statement and does not return a value.
val result = if (age >= 18) "Adult" else "Minor"
println(result) // Output: Adult
✅ when – Kotlin’s Switch Alternative
The when statement in Kotlin is a more flexible alternative to the switch statement in other languages. It can match values, ranges, and even complex conditions.
Basic Usage
val day = 3
when (day) {
1 -> println("Monday")
2 -> println("Tuesday")
3 -> println("Wednesday")
4 -> println("Thursday")
5 -> println("Friday")
else -> println("Weekend")
}
Using when with a Range
You can use ranges in when to check if a value falls within a range.
val number = 5
when (number) {
in 1..5 -> println("Between 1 and 5")
in 6..10 -> println("Between 6 and 10")
else -> println("Out of range")
}
Using when with Complex Conditions
You can also use when with more complex conditions.
val x = 10
when {
x < 5 -> println("Less than 5")
x == 10 -> println("Equal to 10")
else -> println("Other")
}
2. Loops in Kotlin
Loops allow you to execute a block of code multiple times. Kotlin provides three types of loops: for, while, and do-while.
✅ for Loop
The for loop in Kotlin is used to iterate over ranges, arrays, or collections. It’s often used when you know the number of iterations in advance.
Using for with a Range
for (i in 1..5) {
println(i) // Output: 1 2 3 4 5
}
Using for with a Step
You can add a step to the loop, specifying the increment.
for (i in 1..10 step 2) {
println(i) // Output: 1 3 5 7 9
}
Using for with DownTo
You can use the downTo keyword to iterate in reverse.
for (i in 5 downTo 1) {
println(i) // Output: 5 4 3 2 1
}
✅ while Loop
The while loop executes a block of code as long as the condition is true. It’s commonly used when the number of iterations is not known in advance.
var count = 1
while (count <= 5) {
println(count) // Output: 1 2 3 4 5
count++
}
✅ do-while Loop
The do-while loop is similar to the while loop but guarantees that the code will run at least once, even if the condition is false initially.
var count = 1
do {
println(count) // Output: 1 2 3 4 5
count++
} while (count <= 5)
3. Break and Continue Statements
Kotlin provides two control flow statements that can be used inside loops: break and continue.
✅ break
The break statement is used to exit a loop prematurely.
for (i in 1..10) {
if (i == 6) break
println(i) // Output: 1 2 3 4 5
}
✅ continue
The continue statement is used to skip the current iteration and move to the next one.
for (i in 1..10) {
if (i == 6) continue
println(i) // Output: 1 2 3 4 5 7 8 9 10
}
4. Best Practices for Control Flow
Here are some best practices for using control flow in Kotlin:
✅ Use when for multiple conditions: when is often more readable than multiple if-else chains.
✅ Use ranges and collections with loops: Kotlin provides easy ways to loop over ranges and collections, which makes your code cleaner.
✅ Avoid infinite loops: Ensure that the condition for while and do-while loops eventually becomes false, or the program will run indefinitely.
✅ Don’t overuse !! operator: In conditions, avoid using the !! operator for null safety, as it can cause runtime crashes. Use ?. or ?: instead.
Conclusion
In this post, you learned:
✅ How to use if, else, and when for conditional branching.
✅ The different types of loops in Kotlin: for, while, and do-while.
✅ How to control loop execution using break and continue.
🎯 Next Post: Kotlin Functions – How to Write and Call Functions in Kotlin
