Examples & Exercises

All runnable code for the guide lives here. Examples are split into two independent Gradle builds so you only need the Android SDK for the Android parts:

Build	Path	Needs	Covers
Core (JVM)	examples/core/	JDK 17 only	Parts 1–6 and the CLI capstone
Android	examples/android/	JDK 17 + Android SDK	Parts 7–9

Dependency versions are centralized per build in gradle/libs.versions.toml (a Gradle version catalog). The Gradle wrapper is committed, so you do not need Gradle installed.

Building

# Core (JVM) examples
cd examples/core
./gradlew build          # compiles every example and runs its unit tests
./gradlew :hello:run     # run a single example

# Android examples
cd examples/android
./gradlew :app:assembleDebug          # build the app
./gradlew :app:testDebugUnitTest      # run JVM unit tests

CI coverage. The Build examples workflow builds the site, the core examples, and the Android examples (unit tests). Instrumented/emulator tests are run locally only and are not executed in CI — chapters that include them say so explicitly.

Exercise & solution convention

Each chapter ends with an ## Exercises section. Solutions are provided two ways so you can check your work without spoilers:

1. Inline, collapsible answer in the chapter (Markdown source shown below):

## Exercises

1. Write a function `isPalindrome(s: String): Boolean`.

<details>
<summary>Solution</summary>

```kotlin
fun isPalindrome(s: String): Boolean = s == s.reversed()
```

</details>

1. A compiled solution file under the part’s example module, in a solutions/ source set or package (e.g. examples/core/<part>/src/test/kotlin/.../solutions/). Solution code is compiled and tested by CI, so every published answer is guaranteed to work.

When you add an exercise, add its solution in both places.