Vararg Parameters in Kotlin

Introduction

Vararg Parameters is a fundamental concept every Kotlin developer should understand. Functions are first-class in Kotlin — parameters, return types, and concise syntax make APIs easy to read and reuse.

A vararg parameter accepts zero or more values of the same type. 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 vararg parameter accepts zero or more values of the same type.
• Inside the function, a vararg is treated as an array (Array or typed array).
• Use the spread operator * to pass an array into a vararg parameter.

Syntax

fun sum(vararg numbers: Int): Int

Vararg Parameters in Kotlin Example Program in Kotlin

fun sum(vararg numbers: Int): Int {
    var total = 0
    for (n in numbers) total += n
    return total
}

fun main() {
    println(sum(1, 2, 3))
    println(sum(10, 20))
}

Sample Output

6
30

When to use

Use default and named parameters to reduce overloads; use single-expression functions for small pure helpers.

How it works

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

2. A vararg parameter accepts zero or more values of the same type.

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 vararg parameter accepts zero or more values of the same type.
• 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 vararg parameter accepts zero or more values of the same type.
• Inside the function, a vararg is treated as an array (Array or typed array).
• Use the spread operator * to pass an array into a vararg parameter.
• 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.