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Kotlin Lists

Keep an ordered set of hire records with an explicit mutation policy.

How it works

List exposes read operations, while MutableList also exposes changes. A read-only view is not necessarily an immutable snapshot: the same underlying list may be changed through another reference. toList makes a separate list structure, but its element objects are still shared.

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 lists.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 lists.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 lists.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

lists.kt

package bhylu.lessons.k_lists

fun main() {
    val owned = mutableListOf("B-31", "B-18")
    val view: List<String> = owned
    val snapshot = owned.toList()
    owned.add("B-42")
    println(view)
    println(snapshot)
}

Expected result

[B-31, B-18, B-42]
[B-31, B-18]

The view sees the added identifier; the copied list does not. Since these elements are immutable strings, a shallow element copy is enough for this fixture. Mutable record elements would require another ownership decision.

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

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