Labeled Return in Kotlin

Introduction

Labeled Return is a fundamental concept every Kotlin developer should understand. Loops repeat code blocks; break, continue and labels give fine-grained control over iteration flow.

A label lets you return from a specific function or loop, not just the innermost lambda. In this tutorial you will learn the syntax, walk through a complete example program, study the sample output, and review best practices so you can apply the concept confidently in your own projects.

Definition

• A label lets you return from a specific function or loop, not just the innermost lambda.
• Use return@label to exit a lambda passed to forEach, apply, or a custom function.
• Labels improve control flow in nested lambdas without non-local returns everywhere.

Syntax

list.forEach {
    if (it < 0) return@forEach
    println(it)
}

Labeled Return in Kotlin Example Program in Kotlin

fun main() {
    val numbers = listOf(1, -2, 3, -4, 5)
    numbers.forEach { value ->
        if (value < 0) return@forEach
        println(value)
    }
    println("Done")
}

Sample Output

1
3
5
Done

When to use

Use break to exit early when a condition is met; use continue to skip invalid items in a collection loop.

How it works

1. The program starts with a main function — the entry point that runs when you execute the file.

2. A label lets you return from a specific function or loop, not just the innermost lambda.

3. Run the program in IntelliJ IDEA, Android Studio, or with the Kotlin command-line compiler (kotlinc / kotlin). Compare your console output with the sample output shown below.

Best Practices

• Understand the core idea: a label lets you return from a specific function or loop, not just the innermost lambda.
• Prefer readable names and small functions so examples map directly to real projects.
• Run and modify the example — change values and observe how the output changes.

Common Mistakes

• Skipping the example and only reading the definition — hands-on practice cements the concept.
• Copying syntax without understanding nullable vs non-nullable types or scope rules.
• Ignoring compiler warnings that often point to safer alternatives.

Key Points

• A label lets you return from a specific function or loop, not just the innermost lambda.
• Use return@label to exit a lambda passed to forEach, apply, or a custom function.
• Labels improve control flow in nested lambdas without non-local returns everywhere.
• Test the example locally and verify the output matches the sample.
• Experiment by changing input values to see how behaviour changes.

Notes

• Semicolons at the end of statements are optional in Kotlin.