bhylu.com

Advertisements

Kotlin Filter and Map

Select ready bicycles, then transform them into display labels.

How it works

filter keeps matching elements and map transforms each selected element. Ordinary collection operations are eager: their results are computed when the call happens. A clear pipeline is often easier to inspect than a loop that mixes selection, conversion and output.

Run this Kotlin example

These are local Kotlin/JVM programs. Install a JDK and the compiler using the official Kotlin compiler guide, or use an IDE with Kotlin support. Check java -version and kotlinc -version in a new terminal. The reviewed compiler is Kotlin 2.4.21 with a JVM 21 target, executed on Temurin JDK 25.0.5. Use JDK 21 or newer for this target. Android, Kotlin/JS and Kotlin/Native require separate platform projects and are not the tested environment here.

Save the complete source as filter-map.kt in its own learning folder. The package line gives this example a namespace, not a network address. Bhylu has no Kotlin browser runner; do not use the JavaScript or Python editor. Apache, PHP and MySQL are not required.

Compile with kotlinc filter-map.kt -jvm-target 21 -include-runtime -d lesson.jar, then run java -jar lesson.jar. Use a learning folder you own and keep generated JARs outside the website. These sources require no third-party application libraries.

Download the complete filter-map.kt · Download all source files with hash checks

For the optional collection, save download-examples.mjs in a new learning folder and run node download-examples.mjs. A local preview uses node download-examples.mjs http://127.0.0.1:8000/examples/kotlin/. It refuses an existing bhylu-kotlin-examples folder and installs or executes no Kotlin code. Compile one ordinary lesson at a time by filename.

Example

filter-map.kt

package bhylu.lessons.k_filter_map

fun main() {
    val counts = listOf(0, 3, 1, 0, 2)
    val labels = counts.filter { it > 0 }.map { "$it ready" }
    println(labels)
}

Expected result

[3 ready, 1 ready, 2 ready]

it is the single implicit lambda parameter. The filter removes zeros before map builds text. The source list remains unchanged, and its surviving order is preserved.

For exact language and library contracts, consult the official Kotlin documentation. These fictional fixtures are learning programs, not a deployed hire service.

Advertisements