Kotlin - 将列表转换为 MutableList 的最普通方式
原标题：Kotlin - Most idiomatic way to convert a List to a MutableList
I have a method (getContacts) that returns a List and I need to convert this result to a MutableList. Currently the best way I can think of doing it is like this:
val contacts: MutableList = ArrayList(presenter.getContacts())
Is there a more idiomatic/"less Java" way to do that?
最佳回答
Consider using the toMutableList() function:
presenter.getContacts().toMutableList()
There are toMutableList() extensions for the stdlib types that one might want to convert to a mutable list: Collection, Iterable, Sequence, CharSequence, Array and primitive arrays.
问题回答
If you only wants ArrayList, you can create your own Kotlin extension.
fun List.toArrayList(): ArrayList{
return ArrayList(this)
}
Then you can use it in your application like
myList.toArrayList()
Simple and easy
You can also use toTypedArray() if you want to convert a List or MutableList to Array
/**
* 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 Collection.toTypedArray(): Array {
@Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
val thisCollection = this as java.util.Collection
return thisCollection.toArray(arrayOfNulls(0)) as Array
}
Example
myMutableList.toTypedArray()
You can use Kotlin s generic function with a return MutableList type:
fun kotlinMutable(list: List): MutableList {
return list.toMutableList()
}
fun main() {
val list: List = listOf("a","b","c","x")
val kml = kotlinMutable(list)
kml.add("y") // [a, b, c, x, y]
for (i in 2 downTo 0 step 1) {
kml.remove(kml[i])
}
println(kml) // [x, y]
}
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