Added in API level 24

KeySetView

open class KeySetView<K : Any!, V : Any!> : MutableCollection<K>, Serializable, MutableSet<K>
kotlin.Any
   ↳ java.util.concurrent.ConcurrentHashMap.KeySetView

A view of a ConcurrentHashMap as a Set of keys, in which additions may optionally be enabled by mapping to a common value. This class cannot be directly instantiated. See keySet(V), newKeySet(), newKeySet(int).

Summary

Public methods
open Boolean
add(element: K)

Adds the specified key to this set view by mapping the key to the default mapped value in the backing map, if defined.

open Boolean
addAll(elements: Collection<K>)

Adds all of the elements in the specified collection to this set, as if by calling add on each one.

Unit

Removes all of the elements from this view, by removing all the mappings from the map backing this view.

open Boolean
contains(element: K)

Returns true if this collection contains the specified element.

Boolean
containsAll(elements: Collection<K>)

open Boolean
equals(other: Any?)

open Unit
forEach(action: Consumer<in K>)

open ConcurrentHashMap<K, V>

Returns the map backing this view.

open V?

Returns the default mapped value for additions, or null if additions are not supported.

open Int

Boolean

open MutableIterator<K>

open Boolean
remove(element: K)

Removes the key from this map view, by removing the key (and its corresponding value) from the backing map.

open Boolean
removeAll(elements: Collection<K>)

Boolean
retainAll(elements: Collection<K>)

open Spliterator<K>

Array<Any!>

Array<T>
toArray(a: Array<T>)

String

Returns a string representation of this collection.

Properties
Int

Public methods

add

Added in API level 24
open fun add(element: K): Boolean

Adds the specified key to this set view by mapping the key to the default mapped value in the backing map, if defined.

Parameters
e key to be added
Return
Boolean true if this set changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if no default mapped value for additions was provided
java.lang.ClassCastException if the class of the specified element prevents it from being added to this set
java.lang.NullPointerException if the specified key is null
java.lang.IllegalArgumentException if some property of the specified element prevents it from being added to this set
java.lang.IllegalStateException if the element cannot be added at this time due to insertion restrictions

addAll

Added in API level 24
open fun addAll(elements: Collection<K>): Boolean

Adds all of the elements in the specified collection to this set, as if by calling add on each one.

Parameters
c the elements to be inserted into this set
Return
Boolean true if this set changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if no default mapped value for additions was provided
java.lang.ClassCastException if the class of an element of the specified collection prevents it from being added to this set
java.lang.NullPointerException if the collection or any of its elements are null
java.lang.IllegalArgumentException if some property of an element of the specified collection prevents it from being added to this set
java.lang.IllegalStateException if not all the elements can be added at this time due to insertion restrictions

clear

Added in API level 24
fun clear(): Unit

Removes all of the elements from this view, by removing all the mappings from the map backing this view.

Exceptions
java.lang.UnsupportedOperationException if the clear method is not supported by this set

contains

Added in API level 24
open fun contains(element: K): Boolean

Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that Objects.equals(o, e).

Parameters
o element whose presence in this set is to be tested
Return
Boolean true if this set contains the specified element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this set (optional)
java.lang.NullPointerException if the specified key is null

containsAll

Added in API level 24
fun containsAll(elements: Collection<K>): Boolean
Parameters
c collection to be checked for containment in this set
Return
Boolean true if this set contains all of the elements of the specified collection
Exceptions
java.lang.ClassCastException if the types of one or more elements in the specified collection are incompatible with this set (optional)
java.lang.NullPointerException if the specified collection contains one or more null elements and this set does not permit null elements (optional), or if the specified collection is null

equals

Added in API level 24
open fun equals(other: Any?): Boolean
Parameters
obj the reference object with which to compare.
o object to be compared for equality with this set
Return
Boolean true if the specified object is equal to this set

forEach

Added in API level 24
open fun forEach(action: Consumer<in K>): Unit
Parameters
action Consumer<in K>: The action to be performed for each element
Exceptions
java.lang.NullPointerException if the specified action is null

getMap

Added in API level 24
open fun getMap(): ConcurrentHashMap<K, V>

Returns the map backing this view.

Return
ConcurrentHashMap<K, V> the map backing this view

getMappedValue

Added in API level 24
open fun getMappedValue(): V?

Returns the default mapped value for additions, or null if additions are not supported.

Return
V? the default mapped value for additions, or null if not supported

hashCode

Added in API level 24
open fun hashCode(): Int
Return
Int the hash code value for this set

isEmpty

Added in API level 24
fun isEmpty(): Boolean
Return
Boolean true if this set contains no elements

iterator

Added in API level 24
open fun iterator(): MutableIterator<K>
Return
MutableIterator<K> an iterator over the keys of the backing map

remove

Added in API level 24
open fun remove(element: K): Boolean

Removes the key from this map view, by removing the key (and its corresponding value) from the backing map. This method does nothing if the key is not in the map.

Parameters
o the key to be removed from the backing map
Return
Boolean true if the backing map contained the specified key
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this set (optional)
java.lang.NullPointerException if the specified key is null
java.lang.UnsupportedOperationException if the remove operation is not supported by this set

removeAll

Added in API level 24
open fun removeAll(elements: Collection<K>): Boolean
Parameters
c collection containing elements to be removed from this set
Return
Boolean true if this set changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the removeAll operation is not supported by this set
java.lang.ClassCastException if the class of an element of this set is incompatible with the specified collection (optional)
java.lang.NullPointerException if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null

retainAll

Added in API level 24
fun retainAll(elements: Collection<K>): Boolean
Parameters
c collection containing elements to be retained in this set
Return
Boolean true if this set changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the retainAll operation is not supported by this set
java.lang.ClassCastException if the class of an element of this set is incompatible with the specified collection (optional)
java.lang.NullPointerException if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null

spliterator

Added in API level 24
open fun spliterator(): Spliterator<K>
Return
Spliterator<K> a Spliterator over the elements in this set

toArray

Added in API level 24
fun toArray(): Array<Any!>
Return
Array<Any!> an array containing all the elements in this set

toArray

Added in API level 24
fun <T : Any!> toArray(a: Array<T>): Array<T>
Parameters
<T> the component type of the array to contain the collection
a Array<T>: the array into which the elements of this set are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
Return
Array<T> an array containing all the elements in this set
Exceptions
java.lang.ArrayStoreException if the runtime type of the specified array is not a supertype of the runtime type of every element in this set
java.lang.NullPointerException if the specified array is null

toString

Added in API level 24
fun toString(): String

Returns a string representation of this collection. The string representation consists of the string representations of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String#valueOf(Object).

Return
String a string representation of this collection

Properties

size

Added in API level 24
val size: Int
Return
Int the number of elements in this set (its cardinality)