Print contents of a List separated by comma in Kotlin

This article explores different ways to print contents of a List separated by a comma in Kotlin.

1. Using `joinToString()` function

The standard solution to concatenate all the list elements with a separator is with the joinToString() function.

fun main() {

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

val separator = ", "

val str = list.joinToString(separator)

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

}

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The joinToString() function is overloaded to accept the prefix and postfix as well.

fun main() {

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

val separator = ", "

val prefix = "["

val postfix = "]"

val str = list.joinToString(separator, prefix, postfix)

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

}

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2. Using `String.join()` function

If you don’t mind using Java’s String class, you can use the String.join() function. It connects all strings in a List together with the specified separator.

fun main() {

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

val separator = ", "

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

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

}

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3. Using `StringJoiner` class

Another Java-based solution involves using the StringJoiner class to construct a sequence of elements separated by a separator.

import java.util.StringJoiner

fun main() {

val list = listOf(1, 2, 3, 4, 5)

val separator = ", "

val joiner = StringJoiner(separator)

list.forEach { joiner.add(it.toString()) }

println(joiner.toString()) // 1, 2, 3, 4, 5

}

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To create a string beginning with the given prefix and ending with the given postfix, do like:

import java.util.StringJoiner

fun main() {

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

val separator = ", "

val prefix = "["

val postfix = "]"

val joiner = StringJoiner(separator, prefix, postfix)

list.forEach { joiner.add(it) }

println(joiner.toString()) // [A, B, C, D]

}

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4. Using String builder

The String builder can be used to efficiently perform multiple string manipulation operations. The following code example demonstrates the usage of String builder, to collect contents of a List separated by a comma.

fun main() {

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

val sb = StringBuilder()

var separator = ""

for (s in list) {

sb.append(separator).append(s)

separator = ", "

}

println(sb.toString()) // A, B, C, D

}

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That’s all about printing contents of a List separated by a comma in Kotlin.

Print contents of a List separated by comma in Kotlin

1. Using joinToString() function

2. Using String.join() function

3. Using StringJoiner class

4. Using String builder

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1. Using `joinToString()` function

2. Using `String.join()` function

3. Using `StringJoiner` class