Kotlin Output and Comments

How it works

print writes without a newline, while println adds one. A dollar name or dollar-braced expression inserts a value in a string template. Double slashes start a line comment; slash-star comments can span lines. Use comments for intent rather than repeating obvious syntax.

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 output-comments.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 output-comments.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 output-comments.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

package bhylu.lessons.k_output_comments

fun main() {
    // Keep one bicycle for the maintenance check.
    val fleet = 7
    val reserved = 1
    print("Available: ")
    println(fleet - reserved)
}

Expected result

Available: 6

The two output calls form one line. The comment explains why the reserve exists. A comment cannot enforce the rule; the subtraction is the actual operation.