如何在Kotlin中将Set（HashSet）转换为数组？

Question

我有一套弦乐

 val set = HashSet<String>()
    set.add("a")
    set.add("b")
    set.add("c")

我需要将其转换为数组

val array = arrayOf("a", "b", "c")

Answer 1

按如下所述使用扩展功能toTypedArray

set.toTypedArray()

该功能属于Kotlin库

/**
 * Returns a *typed* array containing all of the elements of this collection.
 *
 * Allocates an array of runtime type `T` having its size equal to the size of this collection
 * and populates the array with the elements of this collection.
 * @sample samples.collections.Collections.Collections.collectionToTypedArray
 */
@Suppress("UNCHECKED_CAST")
public actual inline fun <reified T> Collection<T>.toTypedArray(): Array<T> {
    @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
    val thisCollection = this as java.util.Collection<T>
    return thisCollection.toArray(arrayOfNulls<T>(0)) as Array<T>
}

Answer 2

将集合（HashSet）转换为数组

URLSessionDataTask

运行程序时，输出为：

import java.util.*

fun main(args: Array<String>) {

    val set = HashSet<String>()
    set.add("a")
    set.add("b")
    set.add("c")

    val array = arrayOfNulls<String>(set.size)
    set.toArray(array)

    println("Array: ${Arrays.toString(array)}")

}

Answer 3

仅val array = set.toArray()

Answer 4

您可以致电

val array = set.toArray()

使用Kotlin 1.2.51测试。