Writing Comments

In this lesson you will learn how to write comments in Kotlin so the intent of your code is clear to other people and to your future self. This is for anyone searching for "Kotlin comments syntax".

A comment is a note for humans that has no effect on execution. // starts a single-line comment and /* */ wraps a multi-line one.

The sample code shows all three patterns: a whole-line comment such as // This is a single-line comment, a trailing note as in val price = 100 // product price, and a multi-line comment enclosed in /* */.

A common stumbling block for beginners is writing so many comments that the code gets harder to read. Recording why a piece of logic is needed is valuable; restating what the code already says is not.

In real-world development, a special form called KDoc lets tools generate function documentation automatically.

📖 Reference code

fun main() {
    // This is a single-line comment
    val price = 100 // product price

    /*
       This is a
       multi-line comment
    */
    println("Price: ${price}")
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).