How to append strings separated by a comma in Kotlin

This article explores different ways to append strings separated by a comma in Kotlin.

There are several ways to convert a collection to a comma-separated String in Kotlin:

1. Using `joinToString()` function

The standard solution to join elements of a list with the specified delimiter is using the joinToString() function. Its usage is demonstrated below:

fun main() {

val input = listOf(1, 2, 3, 4)

val separator = ", "

val str = input.joinToString(separator, transform = Int::toString)

println(str) // 1, 2, 3, 4

}

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You can customize the output to our style as follows:

fun main() {

val input = listOf(1, 2, 3, 4)

val str = input.joinToString(

prefix = "[",

separator = ", ",

postfix = "]",

limit = 3,

truncated = "...",

transform = Int::toString

)

println(str) // [1, 2, 3, ...]

}

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2. Using `toString()` function

The toString() function returns the string representation of the collection, which consists of all its elements, enclosed in square brackets [], and adjacent elements separated by the delimiter ", ".

fun main() {

val input = listOf(1, 2, 3, 4)

val str = input.toString()

println(str) // [1, 2, 3, 4]

}

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3. Using `String.join()` function

Another possibility to join strings together with a specified separator is with the java.lang.String.join() function, which only works for an Iterable<String>

fun main() {

val words = listOf("A", "B", "C", "D")

val separator = ", "

val str = java.lang.String.join(separator, words)

println(str) // A, B, C, D

}

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4. Using String builder

Finally, you can create a utility function to traverse the list and append each element to a String builder with the specified delimiter. This logic would translate to the following code:

fun <T> join(list: List<T>): String {

val sb = StringBuilder()

var sep = ""

for (e in list) {

sb.append(sep).append(e)

sep = ","

}

return sb.toString()

}

fun main() {

val words = listOf("Hello", "World")

val str = join(words)

println(str) // Hello,World

}

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That’s all about appending strings separated by a comma in Kotlin.

How to append strings separated by a comma in Kotlin

1. Using joinToString() function

2. Using toString() function

3. Using String.join() function

4. Using String builder

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1. Using `joinToString()` function

2. Using `toString()` function

3. Using `String.join()` function