String templates and interpolation in Kotlin

Introduction

String templates let you put values right inside text easily. This makes your messages clear and quick to write.

When you want to show a user's name inside a greeting message.

When you need to include numbers or results inside a sentence.

When building dynamic messages that change based on data.

When formatting output for logs or reports with variable info.

Syntax

Kotlin

val message = "Hello, $name!"
val info = "You have ${count + 1} new messages."

Use $variableName to insert simple variables.

Use ${expression} to insert calculations or more complex code.

Examples

Insert a simple variable name inside the string.

Kotlin

val name = "Anna"
val greeting = "Hi, $name!"

Calculate sum inside the string using ${}.

Kotlin

val apples = 3
val oranges = 5
val total = "Total fruits: ${apples + oranges}"

Use \$ to show a literal dollar sign before a variable.

Kotlin

val price = 9.99
val message = "Price is \$$price"

Sample Program

This program uses string templates to show a greeting with the user's name, number of items, and total cost. It also shows how to print a dollar sign.

Kotlin

fun main() {
    val user = "Sam"
    val items = 4
    val pricePerItem = 2.5
    val totalCost = items * pricePerItem

    val message = "Hello, $user! You bought $items items. Total cost: \$$totalCost"
    println(message)
}

Important Notes

Remember to escape the dollar sign \$ if you want it to appear as a normal character.

String templates work only inside double quotes "", not single quotes.

Summary

String templates let you put variables or expressions inside strings easily.

Use $variable for simple variables and ${expression} for calculations.

Escape dollar signs with \$ to show them literally.