---
title: "Kotlin Coding Style"
description: "> This file extends the common coding style rule with Kotlin-specific content."
type: skill
canonical_url: https://claudary.paisolsolutions.com/skills/kotlin-coding-style
source: "Claudary"
difficulty: intermediate
author: "Claude Code Knowledge Pack"
date: 2026-07-10T11:30:26.149Z
license: CC-BY-4.0
attribution: "Kotlin Coding Style — Claudary (https://claudary.paisolsolutions.com/skills/kotlin-coding-style)"
---

# Kotlin Coding Style
> This file extends the common coding style rule with Kotlin-specific content.

## Overview

---
description: "Kotlin coding style extending common rules"
globs: ["**/*.kt", "**/*.kts", "**/build.gradle.kts"]
alwaysApply: false
---
# Kotlin Coding Style

> This file extends the common coding style rule with Kotlin-specific content.

## Formatting

- Auto-formatting via **ktfmt** or **ktlint** (configured in `kotlin-hooks.md`)
- Use trailing commas in multiline declarations

## Immutability

The global immutability requirement is enforced in the common coding style rule.
For Kotlin specifically:

- Prefer `val` over `var`
- Use immutable collection types (`List`, `Map`, `Set`)
- Use `data class` with `copy()` for immutable updates

## Null Safety

- Avoid `!!` -- use `?.`, `?:`, `require`, or `checkNotNull`
- Handle platform types explicitly at Java interop boundaries

## Expression Bodies

Prefer expression bodies for single-expression functions:

```kotlin
fun isAdult(age: Int): Boolean = age >= 18
```

## Reference

See skill: `kotlin-patterns` for comprehensive Kotlin idioms and patterns.

---

Source: [Claudary](https://claudary.paisolsolutions.com/skills/kotlin-coding-style) · https://claudary.paisolsolutions.com