Strings, characters and templates

A report sentence combines a student name with a score. Kotlin string templates insert variables using a dollar sign and expressions using dollar-brace syntax. Char describes one UTF-16 code unit, whereas String holds a sequence of code units on the JVM.

What you’ll learn

Insert values and expressions into a string template.
Distinguish UTF-16 length from visible characters.

Strings, characters and templates in the example

1
Stored values
A report sentence combines a student name with a score.
```
Stored values
```
→2
Template expression
Double quotes form a String and single quotes form a Char.
```
Template expression
```
→3
Formatted text
The template computes score + 5 before formatting, so the message contains 85.
```
Formatted text
```

The template computes score + 5 before formatting, so the message contains 85. The emoji length is two UTF-16 code units on the JVM, not two visible faces. This is a representation boundary, not an error in the text.

Understand strings, characters and templates

Double quotes form a String and single quotes form a Char. Templates format an expression’s value; they do not evaluate arbitrary text as source code. JVM string length measures UTF-16 code units, which can differ from the number of visible Unicode characters.

Follow strings, characters and templates

Save the complete source as Main.kt and use the Kotlin/JVM environment. No separate input file is needed.

Kotlin/JVM · complete program

fun main() {
  val name = "Diya"
  val score = 80
  println("$name scored ${score + 5}")
  println("😀".length)
}

Expected output

Diya scored 85
2

Follow the execution

The template computes score + 5 before formatting, so the message contains 85. The emoji length is two UTF-16 code units on the JVM, not two visible faces. This is a representation boundary, not an error in the text.

Try this in the Kotlin compiler by pasting the complete program.

Practice: Strings, characters and templates

Your task: Does the displayed bonus change the stored score?

Kotlin/JVM · complete program

fun main() {
  val name = "Diya"
  val score = 80
  println("$name scored ${score + 5}")
  println("😀".length)
}

Worked answer

No. The expression calculates a value for the message without assigning it back. Score remains 80.