joinToString

Начиная с Kotlin: 1.0

fun <T> Array<out T>.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (T) -> CharSequence? = null): String

fun ByteArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Byte) -> CharSequence? = null): String

fun ShortArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Short) -> CharSequence? = null): String

fun IntArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Int) -> CharSequence? = null): String

fun LongArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Long) -> CharSequence? = null): String

fun FloatArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Float) -> CharSequence? = null): String

fun DoubleArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Double) -> CharSequence? = null): String

fun BooleanArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Boolean) -> CharSequence? = null): String

fun CharArray.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (Char) -> CharSequence? = null): String

fun <T> Iterable<T>.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (T) -> CharSequence? = null): String

Создаёт строку из всех элементов, разделённых с помощью separator, и использует указанные prefix и postfix, если они заданы.

Если коллекция не содержит элементов, результат состоит только из prefix, за которым следует postfix (по умолчанию оба значения пусты).

Если коллекция очень большая, можно указать неотрицательное значение limit. В этом случае будут добавлены только первые limit элементов, за которыми последует строка truncated (по умолчанию — "...").

Примеры

import kotlin.math.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   val numbers = listOf(1, 2, 3, 4, 5, 6)
println(numbers.joinToString()) // 1, 2, 3, 4, 5, 6
println(numbers.joinToString(prefix = "[", postfix = "]")) // [1, 2, 3, 4, 5, 6]
println(numbers.joinToString(prefix = "<", postfix = ">", separator = "•")) // <1•2•3•4•5•6>

val chars = charArrayOf('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q')
println(chars.joinToString(limit = 5, truncated = "...!") { it.uppercaseChar().toString() }) // A, B, C, D, E, ...!

// If the receiver is empty, the result only contains prefix and postfix
println("emptyList<Int>().joinToString().isEmpty() is ${emptyList<Int>().joinToString().isEmpty()}") // true
println(emptyList<Int>().joinToString(prefix = "[", postfix = "]")) // [] 
   //sampleEnd
}