Strings and String Templates

A string is a piece of text in double quotes.

String templates

Put $name inside a string to insert a variable's value, or ${ ... } to insert the result of any expression:

fun main() {
    val name = "Ada"
    val age = 36

    println("Hello, $name!")
    println("Next year you'll be ${age + 1}.")
    println("Your name has ${name.length} letters")
    println("Price: \$5")
}

Hello, Ada!
Next year you'll be 37.
Your name has 3 letters
Price: $5

Templates convert any value to text for you. \$ prints a literal dollar sign.

Joining with + also works, as long as the left side is a string:

fun main() {
    val first = "Ada"
    println(first + " Lovelace")
    println("Age: " + 36)
}

Ada Lovelace
Age: 36

Templates are usually clearer than +, especially with several values.

Escape characters

• \n — new line
• \t — tab
• \" — a double quote
• \\ — a backslash

Raw strings

Triple quotes create a raw string: escape characters aren't processed, and it can span several lines. trimIndent() removes the common indentation:

fun main() {
    val name = "Ada"
    val message = """
        Dear $name,
        Thanks for signing up.
    """.trimIndent()
    println(message)
}

Dear Ada,
Thanks for signing up.

Templates still work inside raw strings.

Common mistakes

• Writing "$name.length" and expecting the length — Kotlin inserts name and then prints .length as text. Use "${name.length}".
• 36 + " years" — a number on the left can't be joined to a string with +. Use a template: "$age years".

Practice

Store a product name and a price, then print Coffee costs $3.5 using a template.

fun main() {
    val product = "Coffee"
    val price = 3.5
    println("$product costs \$$price")
}

Coffee costs $3.5