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Kotlin Strings

Build a receipt without confusing text length with a visual character count.

How it works

A String is immutable. String templates insert values and expressions, and functions such as trim and lowercase return new strings. On the JVM, length counts UTF-16 code units; it is not a reliable count of user-perceived characters for every Unicode string.

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 strings.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 strings.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 strings.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

strings.kt

package bhylu.lessons.k_strings

fun main() {
    val raw = "  Canal Gate  "
    val label = raw.trim()
    println("$label: ${label.length}")
    println(label.replace("Gate", "Desk"))
}

Expected result

Canal Gate: 10
Canal Desk

trim removes surrounding whitespace from a new value. replace also returns new text. Keep machine identifiers and display labels separate if normalisation changes have business meaning.

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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