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Kotlin Standard Library for JVM
@file:kotlin.jvm.JvmMultifileClass
@file:kotlin.jvm.JvmName("CollectionsKt")
package kotlin
import java.io.Serializable
import java.util.*
internal object EmptyIterator : ListIterator {
override fun hasNext(): Boolean = false
override fun hasPrevious(): Boolean = false
override fun nextIndex(): Int = 0
override fun previousIndex(): Int = -1
override fun next(): Nothing = throw NoSuchElementException()
override fun previous(): Nothing = throw NoSuchElementException()
}
internal object EmptyList : List, Serializable {
override fun equals(other: Any?): Boolean = other is List<*> && other.isEmpty()
override fun hashCode(): Int = 1
override fun toString(): String = "[]"
override val size: Int get() = 0
override fun isEmpty(): Boolean = true
override fun contains(element: Nothing): Boolean = false
override fun containsAll(elements: Collection): Boolean = elements.isEmpty()
override fun get(index: Int): Nothing = throw IndexOutOfBoundsException("Index $index is out of bound of empty list.")
override fun indexOf(element: Nothing): Int = -1
override fun lastIndexOf(element: Nothing): Int = -1
override fun iterator(): Iterator = EmptyIterator
override fun listIterator(): ListIterator = EmptyIterator
override fun listIterator(index: Int): ListIterator {
if (index != 0) throw IndexOutOfBoundsException("Index: $index")
return EmptyIterator
}
override fun subList(fromIndex: Int, toIndex: Int): List {
if (fromIndex == 0 && toIndex == 0) return this
throw IndexOutOfBoundsException("fromIndex: $fromIndex, toIndex: $toIndex")
}
private fun readResolve(): Any = EmptyList
}
internal fun Array.asCollection(): Collection = ArrayAsCollection(this)
private class ArrayAsCollection(val values: Array): Collection {
override val size: Int get() = values.size
override fun isEmpty(): Boolean = values.isEmpty()
override fun contains(element: T): Boolean = values.contains(element)
override fun containsAll(elements: Collection): Boolean = elements.all { contains(it) }
override fun iterator(): Iterator = values.iterator()
// override hidden toArray implementation to prevent copying of values array
public fun toArray(): Array = values.varargToArrayOfAny()
}
/** Returns an empty read-only list. The returned list is serializable (JVM). */
public fun emptyList(): List = EmptyList
/** Returns a new read-only list of given elements. The returned list is serializable (JVM). */
public fun listOf(vararg elements: T): List = if (elements.size > 0) elements.asList() else emptyList()
/** Returns an empty read-only list. The returned list is serializable (JVM). */
public fun listOf(): List = emptyList()
/**
* Returns an immutable list containing only the specified object [element].
* The returned list is serializable.
*/
@JvmVersion
public fun listOf(element: T): List = Collections.singletonList(element)
/** Returns a new [LinkedList] with the given elements. */
@JvmVersion
public fun linkedListOf(vararg elements: T): LinkedList
= if (elements.size == 0) LinkedList() else LinkedList(ArrayAsCollection(elements))
/** Returns a new [ArrayList] with the given elements. */
public fun arrayListOf(vararg elements: T): ArrayList
= if (elements.size == 0) ArrayList() else ArrayList(ArrayAsCollection(elements))
/** Returns a new read-only list either of single given element, if it is not null, or empty list it the element is null. The returned list is serializable (JVM). */
public fun listOfNotNull(element: T?): List = if (element != null) listOf(element) else emptyList()
/** Returns a new read-only list only of those given elements, that are not null. The returned list is serializable (JVM). */
public fun listOfNotNull(vararg elements: T?): List = elements.filterNotNull()
/**
* Returns an [IntRange] of the valid indices for this collection.
*/
public val Collection<*>.indices: IntRange
get() = 0..size - 1
/**
* Returns the index of the last item in the list or -1 if the list is empty.
*
* @sample test.collections.ListSpecificTest.lastIndex
*/
public val List.lastIndex: Int
get() = this.size - 1
/** Returns `true` if the collection is not empty. */
public fun Collection.isNotEmpty(): Boolean = !isEmpty()
/** Returns this Collection if it's not `null` and the empty list otherwise. */
public fun Collection?.orEmpty(): Collection = this ?: emptyList()
/** Returns this List if it's not `null` and the empty list otherwise. */
public fun List?.orEmpty(): List = this ?: emptyList()
/**
* Returns a list containing the elements returned by this enumeration
* in the order they are returned by the enumeration.
*/
@JvmVersion
public fun Enumeration.toList(): List = Collections.list(this)
/**
* Returns the size of this iterable if it is known, or `null` otherwise.
*/
public fun Iterable.collectionSizeOrNull(): Int? = if (this is Collection<*>) this.size else null
/**
* Returns the size of this iterable if it is known, or the specified [default] value otherwise.
*/
public fun Iterable.collectionSizeOrDefault(default: Int): Int = if (this is Collection<*>) this.size else default
/** Returns true when it's safe to convert this collection to a set without changing contains method behavior. */
private fun Collection.safeToConvertToSet() = size > 2 && this is ArrayList
/** Converts this collection to a set, when it's worth so and it doesn't change contains method behavior. */
internal fun Iterable.convertToSetForSetOperationWith(source: Iterable): Collection =
when(this) {
is Set -> this
is Collection ->
when {
source is Collection && source.size < 2 -> this
else -> if (this.safeToConvertToSet()) toHashSet() else this
}
else -> toHashSet()
}
/** Converts this collection to a set, when it's worth so and it doesn't change contains method behavior. */
internal fun Iterable.convertToSetForSetOperation(): Collection =
when(this) {
is Set -> this
is Collection -> if (this.safeToConvertToSet()) toHashSet() else this
else -> toHashSet()
}
// copies typed varargs array to array of objects
@JvmVersion
private fun Array.varargToArrayOfAny(): Array
= Arrays.copyOf(this, this.size, Array::class.java)
/**
* Searches this list or its range for the provided [element] index using binary search algorithm.
* The list is expected to be sorted into ascending order according to the Comparable natural ordering of its elements.
*
* If the list contains multiple elements equal to the specified object, there is no guarantee which one will be found.
*/
public fun > List.binarySearch(element: T?, fromIndex: Int = 0, toIndex: Int = size): Int {
rangeCheck(size, fromIndex, toIndex)
var low = fromIndex
var high = toIndex - 1
while (low <= high) {
val mid = (low + high).ushr(1) // safe from overflows
val midVal = get(mid)
val cmp = compareValues(midVal, element)
if (cmp < 0)
low = mid + 1
else if (cmp > 0)
high = mid - 1
else
return mid // key found
}
return -(low + 1) // key not found
}
/**
* Searches this list or its range for the provided [element] index using binary search algorithm.
* The list is expected to be sorted into ascending order according to the specified [comparator].
*
* If the list contains multiple elements equal to the specified object, there is no guarantee which one will be found.
*/
public fun List.binarySearch(element: T, comparator: Comparator, fromIndex: Int = 0, toIndex: Int = size): Int {
rangeCheck(size, fromIndex, toIndex)
var low = fromIndex
var high = toIndex - 1
while (low <= high) {
val mid = (low + high).ushr(1) // safe from overflows
val midVal = get(mid)
val cmp = comparator.compare(midVal, element)
if (cmp < 0)
low = mid + 1
else if (cmp > 0)
high = mid - 1
else
return mid // key found
}
return -(low + 1) // key not found
}
/**
* Searches this list or its range for an index of an element with the provided [key] using binary search algorithm.
* The list is expected to be sorted into ascending order according to the Comparable natural ordering of keys of its elements.
*
* If the list contains multiple elements with the specified [key], there is no guarantee which one will be found.
*/
public inline fun > List.binarySearchBy(key: K?, fromIndex: Int = 0, toIndex: Int = size, crossinline selector: (T) -> K?): Int =
binarySearch(fromIndex, toIndex) { compareValues(selector(it), key) }
// do not introduce this overload --- too rare
//public fun List.binarySearchBy(key: K, comparator: Comparator, fromIndex: Int = 0, toIndex: Int = size(), selector: (T) -> K): Int =
// binarySearch(fromIndex, toIndex) { comparator.compare(selector(it), key) }
/**
* Searches this list or its range for an index of an element for which [comparison] function returns zero.
* The list is expected to be sorted into ascending order according to the provided [comparison].
*
* @param comparison function that compares an element of the list with the element being searched.
*/
public fun List.binarySearch(fromIndex: Int = 0, toIndex: Int = size, comparison: (T) -> Int): Int {
rangeCheck(size, fromIndex, toIndex)
var low = fromIndex
var high = toIndex - 1
while (low <= high) {
val mid = (low + high).ushr(1) // safe from overflows
val midVal = get(mid)
val cmp = comparison(midVal)
if (cmp < 0)
low = mid + 1
else if (cmp > 0)
high = mid - 1
else
return mid // key found
}
return -(low + 1) // key not found
}
/**
* Checks that `from` and `to` are in
* the range of [0..size] and throws an appropriate exception, if they aren't.
*/
private fun rangeCheck(size: Int, fromIndex: Int, toIndex: Int) {
when {
fromIndex > toIndex -> throw IllegalArgumentException("fromIndex ($fromIndex) is greater than toIndex ($toIndex)")
fromIndex < 0 -> throw IndexOutOfBoundsException("fromIndex ($fromIndex) is less than zero.")
toIndex > size -> throw IndexOutOfBoundsException("toIndex ($toIndex) is greater than size ($size).")
}
}
/**
* Returns a single list of all elements from all collections in the given collection.
*/
public fun Iterable>.flatten(): List {
val result = ArrayList()
for (element in this) {
result.addAll(element)
}
return result
}
/**
* Returns a pair of lists, where
* *first* list is built from the first values of each pair from this collection,
* *second* list is built from the second values of each pair from this collection.
*/
public fun Iterable>.unzip(): Pair, List> {
val expectedSize = collectionSizeOrDefault(10)
val listT = ArrayList(expectedSize)
val listR = ArrayList(expectedSize)
for (pair in this) {
listT.add(pair.first)
listR.add(pair.second)
}
return listT to listR
}