Project structure and build basics in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the main function in Kotlin.

Kotlin

fun [1]() {
    println("Hello, Kotlin!")
}

Drag options to blanks, or click blank then click option'

Aexecute

Bstart

Cmain

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name like 'start' or 'run' which won't be recognized as the entry point.

The main function in Kotlin must be named main to serve as the entry point of the program.

2fill in blank

medium

Complete the code to define a Kotlin source file path inside the standard project structure.

Kotlin

src/[1]/kotlin/com/example/app/Main.kt

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Amain

Btest

Cresources

Djava

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'test' or 'resources' folder for main source files.

In Kotlin projects, source files are usually placed under src/main/kotlin following the standard Gradle project structure.

3fill in blank

hard

Fix the error in the Gradle build script to apply the Kotlin plugin.

Kotlin

plugins {
    id("[1]") version "1.8.0"
}

Drag options to blanks, or click blank then click option'

Ajava

Bkotlin-android

Capplication

Dkotlin-jvm

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'java' plugin id which is for Java projects.

Using 'kotlin-android' for non-Android projects.

The correct plugin id for Kotlin JVM projects is kotlin-jvm. This enables Kotlin support for JVM targets.

4fill in blank

hard

Fill both blanks to create a Kotlin data class with two properties.

Kotlin

data class User(val [1]: String, val [2]: Int)

Drag options to blanks, or click blank then click option'

Aname

Bage

Cemail

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using properties with wrong types or unrelated names.

The data class User has two properties: name of type String and age of type Int.

5fill in blank

hard

Fill all three blanks to create a Gradle dependency declaration for Kotlin standard library.

Kotlin

dependencies {
    implementation("org.jetbrains.kotlin:[1]:[2]")
    testImplementation("org.jetbrains.kotlin:kotlin-test:[3]")
}

Drag options to blanks, or click blank then click option'

Akotlin-stdlib

B1.8.0

Dkotlin-reflect

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong library names or mismatched versions.

The Kotlin standard library dependency is kotlin-stdlib with version 1.8.0. The test dependency uses kotlin-test with the same version.

Practice

1. Which folder in a typical Kotlin project contains the main source code files?

easy

A. resources/main

B. src/test/kotlin

C. build/libs

D. src/main/kotlin

Solution

1. Step 1: Understand standard Kotlin project folders

   The src/main/kotlin folder is where the main Kotlin source files are placed.

2. Step 2: Differentiate from other folders

   src/test/kotlin is for test code, build/libs is for compiled output, and resources/main is for resource files.

3. Final Answer:

   src/main/kotlin -> Option D

4. Quick Check:

   Main source code folder = src/main/kotlin [OK]

Hint: Main code is always under src/main/kotlin folder [OK]

Common Mistakes:

• Confusing test folder with main source folder
• Thinking build output folders contain source code
• Mixing resource folders with source code folders

2. Which file is commonly used to define build instructions in a Kotlin project using Gradle?

easy

A. settings.gradle

B. build.gradle.kts

C. gradle.properties

D. manifest.xml

Solution

1. Step 1: Identify Gradle build script files

   Gradle uses build.gradle.kts (Kotlin DSL) or build.gradle (Groovy DSL) to define build instructions.

2. Step 2: Differentiate from other Gradle-related files

   settings.gradle configures multi-project builds, gradle.properties holds properties, and manifest.xml is unrelated.

3. Final Answer:

   build.gradle.kts -> Option B

4. Quick Check:

   Build instructions file = build.gradle.kts [OK]

Hint: Build scripts are named build.gradle.kts for Kotlin DSL [OK]

Common Mistakes:

• Confusing settings.gradle with build.gradle.kts
• Thinking gradle.properties contains build logic
• Mixing XML files with Gradle scripts

3. Given this Gradle build snippet, what will be the output directory for compiled Kotlin classes?

kotlin {
    jvmToolchain(17)
}

tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
    kotlinOptions.jvmTarget = "17"
}

medium

A. build/classes/kotlin/main

B. src/main/kotlin

C. build/libs

D. out/production

Solution

1. Step 1: Understand Gradle default output folders

   By default, Kotlin compiled classes go to build/classes/kotlin/main for the main source set.

2. Step 2: Differentiate source and output folders

   src/main/kotlin is source code, build/libs holds packaged jars, and out/production is not standard for Gradle Kotlin projects.

3. Final Answer:

   build/classes/kotlin/main -> Option A

4. Quick Check:

   Compiled classes output = build/classes/kotlin/main [OK]

Hint: Compiled classes go under build/classes/kotlin/main by default [OK]

Common Mistakes:

• Confusing source folder with output folder
• Thinking build/libs holds class files instead of jars
• Assuming non-standard output folders

4. You see this error when running Gradle: Could not find method kotlin() for arguments. What is the likely cause?

medium

A. The Kotlin plugin is not applied in build.gradle.kts

B. The source folder is missing

C. The JVM target version is invalid

D. The Gradle wrapper is outdated

Solution

1. Step 1: Understand the error message context

   The error means Gradle does not recognize the kotlin {} block, usually because the Kotlin plugin is missing.

2. Step 2: Check common causes

   Missing plugins { kotlin("jvm") version "x.y.z" } causes this error. Source folder or JVM target issues cause different errors. Outdated Gradle wrapper usually causes version incompatibility errors.

3. Final Answer:

   The Kotlin plugin is not applied in build.gradle.kts -> Option A

4. Quick Check:

   Missing Kotlin plugin causes kotlin() method error [OK]

Hint: Check if Kotlin plugin is applied when kotlin() method errors occur [OK]

Common Mistakes:

• Assuming source folder missing causes this error
• Blaming JVM target version without checking plugin
• Ignoring plugin application in build script

5. You want to add a new resource folder to your Kotlin project for configuration files. Where should you place it to follow standard Gradle project structure?

hard

A. src/resources/main

B. resources/config

C. src/main/resources

D. config/resources

Solution

1. Step 1: Recall standard resource folder location

   Gradle expects resource files in src/main/resources to include them in the build output.

2. Step 2: Differentiate from incorrect folder structures

   Folders like resources/config, src/resources/main, or config/resources are not standard and won't be automatically included.

3. Final Answer:

   src/main/resources -> Option C

4. Quick Check:

   Resource files go under src/main/resources [OK]

Hint: Put resource files in src/main/resources for Gradle to find them [OK]

Common Mistakes:

• Placing resources outside src/main folder
• Using non-standard folder names
• Not including resources in build output