Kotlin Cheat Sheet

Kotlin cheat sheet with real commands and snippets for setup, core workflows, debugging, and production-safe automation patterns. If you are working across tools, pair this with the JSON Cheat Sheet and LaTeX Cheat Sheet.

Setup and Tooling

Goal: Install and verify language toolchain

# Run kotlinc command
kotlinc -version

# Run sdk command
sdk install kotlin

# Run gradle command
gradle -v

Core Workflows

Goal: Run and build source code

# Execute kotlinc workflow
kotlinc Main.kt -include-runtime -d main.jar

# Execute java workflow
java -jar main.jar

Goal: Use a practical code snippet

data class User(val id: Int, val name: String)

fun main() {
    val users = listOf(User(1, "Ada"), User(2, "Linus"))
    println(users.first().name)
}

Testing and Formatting

Goal: Run automated tests

# Execute test-related command
./gradlew test

# Execute test-related command
./gradlew check

Goal: Run lint and formatter checks

# Execute quality command
./gradlew ktlintFormat

# Execute quality command
./gradlew detekt

Automation and CI

Goal: Create a repeatable CI shell step

# Run strict shell mode for CI step
set -euo pipefail

# Install dependencies deterministically
npm ci || pip install -r requirements.txt || true

# Run tests and fail fast on errors
./gradlew test

Debugging and Troubleshooting

Goal: Trace runtime issues

# Print runtime and package manager versions
node --version || python --version || true

# Search stack traces and TODO markers
rg "Traceback|Exception|TODO" .

# Re-run tests with verbose output
./gradlew test -v || ./gradlew test --verbose || true

Common Gotchas

• Pin Kotlin language/runtime versions in local and CI environments.
• Keep formatting and linting automated to avoid noisy diffs in code review.
• Prefer explicit dependency lock files for reproducible builds.
• Write small, deterministic tests that can run quickly in pre-commit checks.
• Document compiler/interpreter flags used in production builds.

Related Sheets

• JSON Cheat Sheet — daily JSON commands and production-ready examples.
• LaTeX Cheat Sheet — daily LaTeX commands and production-ready examples.
• Markdown Cheat Sheet — daily Markdown commands and production-ready examples.