CopyOnWriteArraySet
open class CopyOnWriteArraySet<E : Any!> : AbstractSet<E>, Serializable
kotlin.Any | |||
↳ | java.util.AbstractCollection<E> | ||
↳ | java.util.AbstractSet<E> | ||
↳ | java.util.concurrent.CopyOnWriteArraySet |
A Set
that uses an internal CopyOnWriteArrayList
for all of its operations. Thus, it shares the same basic properties:
- It is best suited for applications in which set sizes generally stay small, read-only operations vastly outnumber mutative operations, and you need to prevent interference among threads during traversal.
- It is thread-safe.
- Mutative operations (
add
,set
,remove
, etc.) are expensive since they usually entail copying the entire underlying array. - Iterators do not support the mutative
remove
operation. - Traversal via iterators is fast and cannot encounter interference from other threads. Iterators rely on unchanging snapshots of the array at the time the iterators were constructed.
Sample Usage. The following code sketch uses a copy-on-write set to maintain a set of Handler objects that perform some action upon state updates.
<code>class Handler { void handle() { ... } } class X { private final CopyOnWriteArraySet<Handler> handlers = new CopyOnWriteArraySet<>(); public void addHandler(Handler h) { handlers.add(h); } private long internalState; private synchronized void changeState() { internalState = ...; } public void update() { changeState(); for (Handler handler : handlers) handler.handle(); } }</code>
This class is a member of the Java Collections Framework.
Summary
Public constructors | |
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Creates an empty set. |
|
CopyOnWriteArraySet(c: MutableCollection<out E>!) Creates a set containing all of the elements of the specified collection. |
Public methods | |
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open Boolean |
add(element: E) Adds the specified element to this set if it is not already present. |
open Boolean |
addAll(elements: Collection<E>) Adds all of the elements in the specified collection to this set if they're not already present. |
open Unit |
clear() Removes all of the elements from this set. |
open Boolean |
contains(element: E?) Returns |
open Boolean |
containsAll(elements: Collection<E>) Returns |
open Boolean |
Compares the specified object with this set for equality. |
open Unit | |
open Boolean |
isEmpty() Returns |
open MutableIterator<E> |
iterator() Returns an iterator over the elements contained in this set in the order in which these elements were added. |
open Boolean |
remove(element: E?) Removes the specified element from this set if it is present. |
open Boolean |
removeAll(elements: Collection<E>) Removes from this set all of its elements that are contained in the specified collection. |
open Boolean | |
open Boolean |
retainAll(elements: Collection<E>) Retains only the elements in this set that are contained in the specified collection. |
open Spliterator<E> |
Returns a |
open Array<Any!> |
toArray() Returns an array containing all of the elements in this set. |
open Array<T> |
Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array. |
Inherited functions | |
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Properties | |
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open Int |
Returns the number of elements in this set. |
Inherited properties | |
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Public constructors
CopyOnWriteArraySet
CopyOnWriteArraySet(c: MutableCollection<out E>!)
Creates a set containing all of the elements of the specified collection.
Parameters | |
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c |
MutableCollection<out E>!: the collection of elements to initially contain |
Exceptions | |
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java.lang.NullPointerException |
if the specified collection is null |
Public methods
add
open fun add(element: E): Boolean
Adds the specified element to this set if it is not already present. More formally, adds the specified element e
to this set if the set contains no element e2
such that Objects.equals(e, e2)
. If this set already contains the element, the call leaves the set unchanged and returns false
.
Parameters | |
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e |
element to be added to this set |
Return | |
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Boolean |
true if this set did not already contain the specified element |
Exceptions | |
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java.lang.UnsupportedOperationException |
if the add operation is not supported by this set |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this set |
java.lang.NullPointerException |
if the specified element is null and this set does not permit null elements |
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
open fun addAll(elements: Collection<E>): Boolean
Adds all of the elements in the specified collection to this set if they're not already present. If the specified collection is also a set, the addAll
operation effectively modifies this set so that its value is the union of the two sets. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress.
Parameters | |
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c |
collection containing elements to be added to this set |
Return | |
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Boolean |
true if this set changed as a result of the call |
Exceptions | |
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java.lang.UnsupportedOperationException |
if the addAll operation is not supported by this set |
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 specified collection is 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 |
See Also
clear
open fun clear(): Unit
Removes all of the elements from this set. The set will be empty after this call returns.
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the clear method is not supported by this set |
contains
open fun contains(element: E?): Boolean
Returns true
if this set contains the specified element. More formally, returns true
if and only if this set contains an element e
such that Objects.equals(o, e)
.
Parameters | |
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o |
element whose presence in this set is to be tested |
Return | |
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Boolean |
true if this set contains the specified element |
Exceptions | |
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java.lang.ClassCastException |
if the type of the specified element is incompatible with this set (optional) |
java.lang.NullPointerException |
if the specified element is null and this set does not permit null elements (optional) |
containsAll
open fun containsAll(elements: Collection<E>): Boolean
Returns true
if this set contains all of the elements of the specified collection. If the specified collection is also a set, this method returns true
if it is a subset of this set.
Parameters | |
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c |
collection to be checked for containment in this set |
Return | |
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Boolean |
true if this set contains all of the elements of the specified collection |
Exceptions | |
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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 is null |
See Also
equals
open fun equals(other: Any?): Boolean
Compares the specified object with this set for equality. Returns true
if the specified object is the same object as this object, or if it is also a Set
and the elements returned by an java.util.Set#iterator() over the specified set are the same as the elements returned by an iterator over this set. More formally, the two iterators are considered to return the same elements if they return the same number of elements and for every element e1
returned by the iterator over the specified set, there is an element e2
returned by the iterator over this set such that Objects.equals(e1, e2)
.
Parameters | |
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obj |
the reference object with which to compare. |
o |
object to be compared for equality with this set |
Return | |
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Boolean |
true if the specified object is equal to this set |
forEach
open fun forEach(action: Consumer<in E>): Unit
Parameters | |
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action |
Consumer<in E>: The action to be performed for each element |
Exceptions | |
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java.lang.NullPointerException |
if the specified action is null |
isEmpty
open fun isEmpty(): Boolean
Returns true
if this set contains no elements.
Return | |
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Boolean |
true if this set contains no elements |
iterator
open fun iterator(): MutableIterator<E>
Returns an iterator over the elements contained in this set in the order in which these elements were added.
The returned iterator provides a snapshot of the state of the set when the iterator was constructed. No synchronization is needed while traversing the iterator. The iterator does NOT support the remove
method.
Return | |
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MutableIterator<E> |
an iterator over the elements in this set |
remove
open fun remove(element: E?): Boolean
Removes the specified element from this set if it is present. More formally, removes an element e
such that Objects.equals(o, e)
, if this set contains such an element. Returns true
if this set contained the element (or equivalently, if this set changed as a result of the call). (This set will not contain the element once the call returns.)
Parameters | |
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o |
object to be removed from this set, if present |
Return | |
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Boolean |
true if this set contained the specified element |
Exceptions | |
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java.lang.ClassCastException |
if the type of the specified element is incompatible with this set (optional) |
java.lang.NullPointerException |
if the specified element is null and this set does not permit null elements (optional) |
java.lang.UnsupportedOperationException |
if the remove operation is not supported by this set |
removeAll
open fun removeAll(elements: Collection<E>): Boolean
Removes from this set all of its elements that are contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.
Parameters | |
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c |
collection containing elements to be removed from this set |
Return | |
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Boolean |
true if this set changed as a result of the call |
Exceptions | |
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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 |
See Also
removeIf
open fun removeIf(filter: Predicate<in E>): Boolean
Parameters | |
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filter |
Predicate<in E>: a predicate which returns true for elements to be removed |
Return | |
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Boolean |
true if any elements were removed |
Exceptions | |
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java.lang.NullPointerException |
if the specified filter is null |
java.lang.UnsupportedOperationException |
if elements cannot be removed from this collection. Implementations may throw this exception if a matching element cannot be removed or if, in general, removal is not supported. |
retainAll
open fun retainAll(elements: Collection<E>): Boolean
Retains only the elements in this set that are contained in the specified collection. In other words, removes from this set all of its elements that are not contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the intersection of the two sets.
Parameters | |
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c |
collection containing elements to be retained in this set |
Return | |
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Boolean |
true if this set changed as a result of the call |
Exceptions | |
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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 |
See Also
spliterator
open fun spliterator(): Spliterator<E>
Returns a Spliterator
over the elements in this set in the order in which these elements were added.
The Spliterator
reports Spliterator.IMMUTABLE
, Spliterator.DISTINCT
, Spliterator.SIZED
, and Spliterator.SUBSIZED
.
The spliterator provides a snapshot of the state of the set when the spliterator was constructed. No synchronization is needed while operating on the spliterator.
Return | |
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Spliterator<E> |
a Spliterator over the elements in this set |
toArray
open fun toArray(): Array<Any!>
Returns an array containing all of the elements in this set. If this set makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
The returned array will be "safe" in that no references to it are maintained by this set. (In other words, this method must allocate a new array even if this set is backed by an array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
Return | |
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Array<Any!> |
an array containing all the elements in this set |
toArray
open fun <T : Any!> toArray(a: Array<T>): Array<T>
Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array. If the set fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this set.
If this set fits in the specified array with room to spare (i.e., the array has more elements than this set), the element in the array immediately following the end of the set is set to null
. (This is useful in determining the length of this set only if the caller knows that this set does not contain any null elements.)
If this set makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
Like the #toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.
Suppose x
is a set known to contain only strings. The following code can be used to dump the set into a newly allocated array of String
:
<code>String[] y = x.toArray(new String[0]);</code>
toArray(new Object[0])
is identical in function to toArray()
.
Parameters | |
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<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 | |
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Array<T> |
an array containing all the elements in this set |
Exceptions | |
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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 |
Properties
size
open val size: Int
Returns the number of elements in this set.
Return | |
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Int |
the number of elements in this set |