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Kotlin Numbers and Conversions

Keep arithmetic range and text parsing separate.

How it works

toLong widens an Int value, while toInt on a Long can discard information. toIntOrNull parses text and gives null on failure; successful parsing still needs domain checks. Integer division removes the fractional part, so select floating-point arithmetic when a fraction is meaningful.

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 numbers-conversions.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 numbers-conversions.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 numbers-conversions.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

numbers-conversions.kt

package bhylu.lessons.k_numbers_conversions

fun main() {
    val bikes = 17
    println("${bikes / 5} ${bikes % 5}")
    val wide = Int.MAX_VALUE.toLong() + 1
    println(wide)
    println("six".toIntOrNull())
}

Expected result

3 2
2147483648
null

The first line reports complete groups and a remainder. Widening occurs before addition. The invalid text is not quietly converted into zero, keeping a missing result distinguishable from a valid zero.

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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