String Templates
In this page:
val text = "Hello $variable"
val text = "Result: ${expression}"
val text = "Value: ${object.property}"Simple Variable Templates
Placing a dollar sign directly before a variable name inside a string, like $name, inserts that variable's current value into the string without needing concatenation.
Example: Simple Variable Templates
// Entry point: execution of the program starts here
fun main() {
// Declare a read-only variable `name`, set to `"Kotlin"`
val name = "Kotlin"
// Declare a read-only variable `version`, set to `2`
val version = 2
// Print "Language: $name, Version: $version" to the console, with a trailing newline
println("Language: $name, Version: $version")
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Expression Templates with Curly Braces
For anything more than a plain variable name -- property access, function calls, or arithmetic -- wrap the expression in ${ } so Kotlin evaluates it and inserts the result.
Example: Expression Templates with Curly Braces
// Entry point: execution of the program starts here
fun main() {
// Declare a read-only variable `a`, set to `5`
val a = 5
// Declare a read-only variable `b`, set to `3`
val b = 3
// Print "Sum: ${a + b}, Product: ${a * b}" to the console, with a trailing newline
println("Sum: ${a + b}, Product: ${a * b}")
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Templates with Object Properties
String templates can reach into an object's properties directly inside ${ }, which is much cleaner than building the string with multiple concatenations.
Example: Templates with Object Properties
// Define a data class `Point`
data class Point(val x: Int, val y: Int)
// Entry point: execution of the program starts here
fun main() {
// Declare a read-only variable `p`, set to `Point(3, 4)`
val p = Point(3, 4)
// Print "Point is at (${p.x}, ${p.y})" to the console, with a trailing newline
println("Point is at (${p.x}, ${p.y})")
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Escaping a Literal Dollar Sign
When a string needs an actual $ character rather than starting a template, escape it with a backslash as \$.
Example: Escaping a Literal Dollar Sign
// Entry point: execution of the program starts here
fun main() {
// Declare a read-only variable `price`, set to `20`
val price = 20
// Print "Price: \$$price" to the console, with a trailing newline
println("Price: \$$price")
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- Forgetting the curly braces around an expression more complex than a single variable, like
$user.nameinstead of${user.name}. - Trying to use string concatenation with
+everywhere out of habit instead of the more readable$variablesyntax. - Forgetting to escape a literal dollar sign with
\$when it should not start a template.
$variableNameinside a string inserts that variable's value directly.${expression}with curly braces is required for anything beyond a simple variable name, such as a property access or a calculation.- A literal dollar sign in a string must be escaped as
\$to avoid being treated as a template. - String templates work inside both single-line and triple-quoted strings.
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