How to Concatenate Strings in Kotlin: Simple Guide

In Kotlin, you can concatenate strings using the + operator or string templates with $variable inside a string. Both methods combine strings easily and clearly in your code.

Syntax

There are two main ways to concatenate strings in Kotlin:

• Using the + operator: Joins two or more strings directly.
• Using string templates: Insert variables or expressions inside a string using $variable or ${expression}.

kotlin

val first = "Hello"
val second = "World"

// Using + operator
val combined1 = first + " " + second

// Using string template
val combined2 = "$first $second"

Example

This example shows how to join two strings using both the + operator and string templates. It prints the combined results.

kotlin

fun main() {
    val greeting = "Hello"
    val name = "Alice"

    // Using + operator
    val message1 = greeting + ", " + name + "!"
    println(message1)

    // Using string template
    val message2 = "$greeting, $name!"
    println(message2)
}

Output

Hello, Alice!
Hello, Alice!

Common Pitfalls

Some common mistakes when concatenating strings in Kotlin include:

• Forgetting spaces between words when using + operator, which causes words to stick together.
• Not using curly braces {} when embedding expressions inside string templates, leading to errors.

kotlin

fun main() {
    val word1 = "Good"
    val word2 = "Morning"

    // Wrong: no space added
    val wrong = word1 + word2
    println(wrong) // Output: GoodMorning

    // Right: add space
    val right = word1 + " " + word2
    println(right) // Output: Good Morning

    val count = 5

    // Wrong: missing braces for expression
    // val message = "Count is $count + 1" // This prints 'Count is 5 + 1'

    // Right: use braces to calculate
    val message = "Count is ${count + 1}"
    println(message) // Output: Count is 6
}

Output

GoodMorning
Good Morning
Count is 6

Quick Reference

Here is a quick summary of string concatenation methods in Kotlin:

Method	Description	Example
+ operator	Joins strings by adding them	"Hello" + " " + "World"
String template	Embed variables or expressions inside strings	"Hello, $name!" or "Sum is ${a + b}"

Key Takeaways

Use the + operator or string templates to concatenate strings in Kotlin.

String templates with $variable are cleaner and easier to read.

Remember to add spaces manually when using + operator.

Use ${} to embed expressions inside string templates.

Both methods produce the same output but string templates are preferred for clarity.