Kotlin Academy · Lesson

String Templates: $variable and ${expression}

Embed variables and expressions inside strings using template syntax.

Lesson 2 of 413 steps

String Templates: $variable and ${expression} is a free Kotlin Academy lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Kotlin Academy learning path, and your progress syncs across the web and the CoddyKit app. The Kotlin Academy course includes 4 lessons in total.

What Are String Templates?

String templates let you embed values directly into a string using $ for simple variables and ${...} for full expressions.

Embedding a Variable

Prefix a variable name with $ inside a string. Kotlin substitutes its value at runtime.

fun main() {
    val name = "Ada"
    println("Hello, $name!") // Hello, Ada!
}

Multiple Variables

Embed as many variables as you need. Each $name is replaced independently.

fun main() {
    val first = "Marie"
    val last = "Curie"
    val year = 1903
    println("$first $last won Nobel in $year")
}

Expressions with ${...}

For anything beyond a single identifier — arithmetic, method calls, property access — use ${expression}.

fun main() {
    val a = 10
    val b = 5
    println("Sum: ${a + b}")
    println("Product: ${a * b}")
}

Calling Methods Inside Templates

Templates can invoke functions and properties. Anything that evaluates to a value works.

fun main() {
    val word = "kotlin"
    println("Length: ${word.length}")
    println("Upper: ${word.uppercase()}")
}

Conditional Expressions

Kotlin if is an expression, so you can embed it directly in a template.

fun main() {
    val score = 75
    println("Result: ${if (score >= 60) "pass" else "fail"}")
}

Escaping the Dollar Sign

If you need a literal $, escape it with a backslash: \$.

fun main() {
    val price = 19
    println("Cost: \$$price") // Cost: $19
}

Nested Templates

You can nest string templates inside ${...}, though deeply nested strings get hard to read.

fun main() {
    val items = listOf("apple", "banana")
    println("List: ${items.joinToString { "[$it]" }}")
}

Templates with Collections

Combine templates with collection operations to format output succinctly.

fun main() {
    val numbers = listOf(1, 2, 3, 4, 5)
    println("Sum of ${numbers.size} numbers: ${numbers.sum()}")
}

Templates and Type Conversion

Any type with a sensible toString() works inside templates — booleans, numbers, custom classes.

data class Point(val x: Int, val y: Int)
fun main() {
    val p = Point(3, 4)
    println("Point: $p") // uses Point.toString()
    println("X coord: ${p.x}")
}

Performance Note

The Kotlin compiler converts string templates to StringBuilder calls, similar to manual concatenation — usually no performance difference. Prefer templates for readability.

fun main() {
    val n = 42
    val a = "Value is $n"       // template
    val b = "Value is " + n      // concatenation
    println(a == b) // true
}

Quick Check

Which template syntax correctly embeds the result of x + 1?

Answer it in the interactive lesson

Recap

Use $variable for simple identifiers and ${expression} for anything more complex. Escape literal dollars with \$. Templates compile to efficient StringBuilder code.

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Frequently Asked Questions

Is the “String Templates: $variable and ${expression}” lesson free?

Yes — any 3 lessons of the Kotlin Academy learning path, including “String Templates: $variable and ${expression}”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Kotlin Academy course includes 4 lessons in total.

What will I learn in “String Templates: $variable and ${expression}”?

Embed variables and expressions inside strings using template syntax. You practise Kotlin Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Kotlin Academy?

No prior experience is required. Kotlin Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “String Templates: $variable and ${expression}” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Kotlin Academy lesson?

Yes. Every Kotlin Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

String Basics: Literals, Escape Sequences & Length
String Templates: $variable and ${expression}
Raw Strings and Triple Quotes
Key String Functions: trim, split, replace, contains

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