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String templates

Learn to embed variables in strings with \$ and \${}.

String templates: $ and ${}

In Kotlin you use the $ sign to embed a variable or expression inside a string. Writing $name inserts the value of the name variable.

For more complex expressions use ${...}: "Sum: ${a + b}". This feature is called a string template and is more readable than string concatenation.

val name = "Alex"
println("Hello $name")          // Hello Alex
println("Sum: ${2 + 3}")         // Sum: 5

Practice Greet the user

Write a fun main(). Inside it declare val name = "Alex". Print Hello $name with println.

Sample solution

Main.kt
fun main() {
    val name = "Alex"
    println("Hello $name")
}

Expected output

Hello Alex

Escaping the dollar sign

In a string template $ is always treated as a variable embed. To write a literal $, escape it with \$: println("Price: \$5") prints Price: $5.

You can also use ${'$'}. Both methods put a real dollar sign in the string safely. Without the escape, Kotlin looks for a variable name after $ and raises a compile error if it cannot find one.

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What does this code print?

Main.kt
val name = "Alex"
println("Hello $name")
  • Hello Alex Correct answer
  • Hello $name
  • Hello val name
  • It throws an error

Explanation: $name is replaced by the value Alex.

2 Complete the expression

Question 
println("Sum: ${____}")
Answer 
println("Sum: ${a + b}")

Explanation: ${a + b} embeds the expression.

3 String templates: match the terms

Term Meaning
$ Variable embed
${} Expression embed
"..." String
println Output

All lessons in Beginner

1 Kotlin basics

  1. What is Kotlin?
  2. Your first program
  3. The main function
  4. Comments
  5. String templates
  6. Summary - Kotlin basics

2 Variables

  1. val and var
  2. Type inference
  3. const
  4. lateinit
  5. by lazy
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. Boolean and Char
  4. String
  5. Any and Unit
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Elvis operator
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String templates
  3. String methods
  4. substring
  5. split and replace
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. if expression
  4. when
  5. when expression
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. Range
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Creating arrays
  2. Array access
  3. Array size
  4. Array loop
  5. Array methods
  6. Summary - Arrays

11 Lists

  1. Creating lists
  2. List operations
  3. List access
  4. List iteration
  5. List methods
  6. Summary - Lists

12 Maps and Sets

  1. Creating sets
  2. Set operations
  3. Creating maps
  4. Map operations
  5. Map iteration
  6. Summary - Maps and Sets

13 Functions

  1. Defining functions
  2. Return values
  3. Expression body
  4. Default parameters
  5. Named arguments
  6. Summary - Functions

14 Null safety

  1. Nullable types
  2. ?, !! and ?:
  3. let
  4. Null check
  5. lateinit
  6. Summary - Null safety

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. Regex
  2. matches and find
  3. replace
  4. StringBuilder
  5. trim and pad
  6. Summary - Advanced strings

17 Enums

  1. enum class
  2. Enum values
  3. Enum properties
  4. when with enum
  5. Enum and range
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. try expression
  5. Custom exceptions
  6. Summary - Exceptions

19 Class basics

  1. class
  2. Constructor
  3. Properties
  4. Methods
  5. this
  6. Summary - Class basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together