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String templates

Learn string templates with \$ and \${}.

String templates

In Kotlin, string templates let you embed a variable or expression inside a String. For a simple variable, the $ prefix is enough.

val name = "Alex"
println("Hello, $name")  // Hello, Alex

You can embed several variables in the same String side by side. Spaces and punctuation stay as they are; only the identifier after $ is replaced by its value.

Templates are more readable than splitting and concatenating text, so they are common in Kotlin.

Embedding expressions with ${}

For a simple variable, $name is enough. But to embed an expression (operation, call) use ${}.

val a = 3
val b = 4
println("Sum: ${a + b}")  // Sum: 7

Inside the braces you can write any Kotlin expression: arithmetic, method call, comparison. The result is converted to a String and embedded.

$name.length does not work; $ only takes name. For the length, write ${name.length}.

Practice Write a greeting with a template

Write a fun main(). Assign "Alex" to val name. Print the template "Hello, $name!" with println.

Starter code

Main.kt
fun main() {
    // Write the greeting
}

Sample solution

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

Expected output

Hello, Alex!

Questions and answers

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

1 Match the template results

Term Meaning
"Hello, $name" Greeting
"Age: $age" Age info
"$a + $b" Two variables
"Done." Fixed text

2 What does "Hello, $name" print? (name = "Alex")

Main.kt
val name = "Alex"
println("Hello, $name")
  • Hello, $name
  • Hello, name
  • Hello, Alex Correct answer
  • Error

Explanation: $name is replaced by the value: Hello, Alex.

3 Complete the expression template

Question 
val msg = "Sum: ____"
Answer 
val msg = "Sum: ${a + b}"

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

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