Assignment operators
- Kotlin course
- Beginner
- Lesson 25/116
- 4 min
Learn shortcut assignments with =, +=, -=, *=, /= and ++/--.
Assignment operators
The = operator assigns a value to a variable. Kotlin also offers compound assignment operators: +=, -=, *=, /=, %=. These perform the operation and the assignment in a single step.
For example, x += 5 is the same as x = x + 5. You can also increment or decrement a variable by one with ++ and --.
var x = 10
x += 5 // x = 15
x -= 3 // x = 12
x++ // x = 13
x-- // x = 12Practice Try compound assignment
Write a fun main(). Declare var total = 10. Increment with total += 5 and print with println(total).
Sample solution
fun main() {
var total = 10
total += 5
println(total)
}Expected output
15
Prefix and postfix ++ and --
The ++ and -- operators can come before or after the variable. ++x increments first then yields the value; x++ yields the value first then increments.
Standalone, both yield the same result. But inside an expression, they differ. So to avoid confusion, prefer standalone use.
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Assignment operators: fill in the missing part
var x = 10
x ____= 5 // x = 15var x = 10
x += 5 // x = 15Explanation: The compound add-assign operator is +=.
2 What does `x += 5` do?
- Adds 5 to x Correct answer
- Sets x to 5
- Multiplies x by 5
- It throws an error
Explanation: The += operator adds 5 to x.
3 Assignment operators: match the terms
| Term | Meaning |
|---|---|
= |
Assign |
+= |
Add and assign |
-= |
Subtract and assign |
++ |
Increment |