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Added in API level 1

CopyOnWriteArrayList

open class CopyOnWriteArrayList<E : Any!> : MutableList<E>, RandomAccess, Cloneable, Serializable
kotlin.Any
   ↳ java.util.concurrent.CopyOnWriteArrayList

A thread-safe variant of java.util.ArrayList in which all mutative operations (add, set, and so on) are implemented by making a fresh copy of the underlying array.

This is ordinarily too costly, but may be more efficient than alternatives when traversal operations vastly outnumber mutations, and is useful when you cannot or don't want to synchronize traversals, yet need to preclude interference among concurrent threads. The "snapshot" style iterator method uses a reference to the state of the array at the point that the iterator was created. This array never changes during the lifetime of the iterator, so interference is impossible and the iterator is guaranteed not to throw ConcurrentModificationException. The iterator will not reflect additions, removals, or changes to the list since the iterator was created. Element-changing operations on iterators themselves (remove, set, and add) are not supported. These methods throw UnsupportedOperationException.

All elements are permitted, including null.

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a CopyOnWriteArrayList happen-before actions subsequent to the access or removal of that element from the CopyOnWriteArrayList in another thread.

Summary

Public constructors

Creates an empty list.

Creates a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

<init>(toCopyIn: Array<E>)

Creates a list holding a copy of the given array.

Public methods
open Boolean
add(element: E)

Appends the specified element to the end of this list.

open Unit
add(index: Int, element: E)

Inserts the specified element at the specified position in this list.

open Boolean
addAll(elements: Collection<E>)

Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator.

open Boolean
addAll(index: Int, elements: Collection<E>)

Inserts all of the elements in the specified collection into this list, starting at the specified position.

open Int

Appends all of the elements in the specified collection that are not already contained in this list, to the end of this list, in the order that they are returned by the specified collection's iterator.

open Boolean

Appends the element, if not present.

open Unit

Removes all of the elements from this list.

open Any

Returns a shallow copy of this list.

open Boolean
contains(element: E?)

Returns true if this list contains the specified element.

open Boolean
containsAll(elements: Collection<E>)

Returns true if this list contains all of the elements of the specified collection.

open Boolean
equals(other: Any?)

Compares the specified object with this list for equality.

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

open E
get(index: Int)

Returns the element at the specified position in this list.

open Int

Returns the hash code value for this list.

open Int
indexOf(e: E?, index: Int)

Returns the index of the first occurrence of the specified element in this list, searching forwards from index, or returns -1 if the element is not found.

open Int
indexOf(element: E?)

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.

open Boolean

Returns true if this list contains no elements.

open MutableIterator<E>

Returns an iterator over the elements in this list in proper sequence.

open Int
lastIndexOf(e: E?, index: Int)

Returns the index of the last occurrence of the specified element in this list, searching backwards from index, or returns -1 if the element is not found.

open Int
lastIndexOf(element: E?)

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.

open MutableListIterator<E>

Returns a list iterator over the elements in this list (in proper sequence).

open MutableListIterator<E>
listIterator(index: Int)

Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.

open Boolean
remove(element: E?)

Removes the first occurrence of the specified element from this list, if it is present.

open Boolean
removeAll(elements: Collection<E>)

Removes from this list all of its elements that are contained in the specified collection.

open E
removeAt(index: Int)

Removes the element at the specified position in this list.

open Boolean
removeIf(filter: Predicate<in E>)

open Unit
replaceAll(operator: UnaryOperator<E>)

open Boolean
retainAll(elements: Collection<E>)

Retains only the elements in this list that are contained in the specified collection.

open E
set(index: Int, element: E)

Replaces the element at the specified position in this list with the specified element.

open Unit
sort(c: Comparator<in E>?)

open Spliterator<E>

Returns a Spliterator over the elements in this list.

open MutableList<E>
subList(fromIndex: Int, toIndex: Int)

Returns a view of the portion of this list between fromIndex, inclusive, and toIndex, exclusive.

open Array<Any!>

Returns an array containing all of the elements in this list in proper sequence (from first to last element).

open Array<T>
toArray(a: Array<T>)

Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.

open String

Returns a string representation of this list.

Properties
open Int

Returns the number of elements in this list.

Public constructors

<init>

Added in API level 1
CopyOnWriteArrayList()

Creates an empty list.

<init>

Added in API level 1
CopyOnWriteArrayList(c: MutableCollection<out E>)

Creates a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Parameters
c MutableCollection<out E>: the collection of initially held elements
Exceptions
java.lang.NullPointerException if the specified collection is null

<init>

Added in API level 1
CopyOnWriteArrayList(toCopyIn: Array<E>)

Creates a list holding a copy of the given array.

Parameters
toCopyIn Array<E>: the array (a copy of this array is used as the internal array)
Exceptions
java.lang.NullPointerException if the specified array is null

Public methods

add

Added in API level 1
open fun add(element: E): Boolean

Appends the specified element to the end of this list.

Parameters
e element to be appended to this list
Return
Boolean true (as specified by Collection#add)
Exceptions
java.lang.UnsupportedOperationException if the add operation is not supported by this list
java.lang.ClassCastException if the class of the specified element prevents it from being added to this list
java.lang.NullPointerException if the specified element is null and this list does not permit null elements
java.lang.IllegalArgumentException if some property of this element prevents it from being added to this list
java.lang.IllegalStateException if the element cannot be added at this time due to insertion restrictions

add

Added in API level 1
open fun add(
    index: Int,
    element: E
): Unit

Inserts the specified element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).

Parameters
index Int: index at which the specified element is to be inserted
element E: element to be inserted
Exceptions
java.lang.UnsupportedOperationException if the add operation is not supported by this list
java.lang.ClassCastException if the class of the specified element prevents it from being added to this list
java.lang.NullPointerException if the specified element is null and this list does not permit null elements
java.lang.IllegalArgumentException if some property of the specified element prevents it from being added to this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

addAll

Added in API level 1
open fun addAll(elements: Collection<E>): Boolean

Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator.

Parameters
c collection containing elements to be added to this list
Return
Boolean true if this list changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the addAll operation is not supported by this list
java.lang.ClassCastException if the class of an element of the specified collection prevents it from being added to this list
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 list
java.lang.IllegalStateException if not all the elements can be added at this time due to insertion restrictions

See Also

addAll

Added in API level 1
open fun addAll(
    index: Int,
    elements: Collection<E>
): Boolean

Inserts all of the elements in the specified collection into this list, starting at the specified position. Shifts the element currently at that position (if any) and any subsequent elements to the right (increases their indices). The new elements will appear in this list in the order that they are returned by the specified collection's iterator.

Parameters
index Int: index at which to insert the first element from the specified collection
c collection containing elements to be added to this list
Return
Boolean true if this list changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the addAll operation is not supported by this list
java.lang.ClassCastException if the class of an element of the specified collection prevents it from being added to this list
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 list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

See Also

addAllAbsent

Added in API level 1
open fun addAllAbsent(c: MutableCollection<out E>): Int

Appends all of the elements in the specified collection that are not already contained in this list, to the end of this list, in the order that they are returned by the specified collection's iterator.

Parameters
c MutableCollection<out E>: collection containing elements to be added to this list
Return
Int the number of elements added
Exceptions
java.lang.NullPointerException if the specified collection is null

addIfAbsent

Added in API level 1
open fun addIfAbsent(e: E): Boolean

Appends the element, if not present.

Parameters
e E: element to be added to this list, if absent
Return
Boolean true if the element was added

clear

Added in API level 1
open fun clear(): Unit

Removes all of the elements from this list. The list will be empty after this call returns.

Exceptions
java.lang.UnsupportedOperationException if the clear operation is not supported by this list

clone

Added in API level 1
open fun clone(): Any

Returns a shallow copy of this list. (The elements themselves are not copied.)

Return
Any a clone of this list
Exceptions
java.lang.CloneNotSupportedException if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.

contains

Added in API level 1
open fun contains(element: E?): Boolean

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

Parameters
o element whose presence in this list is to be tested
Return
Boolean true if this list contains the specified element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

containsAll

Added in API level 1
open fun containsAll(elements: Collection<E>): Boolean

Returns true if this list contains all of the elements of the specified collection.

Parameters
c collection to be checked for containment in this list
Return
Boolean true if this list 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 list (optional)
java.lang.NullPointerException if the specified collection is null

equals

Added in API level 1
open fun equals(other: Any?): Boolean

Compares the specified object with this list for equality. Returns true if the specified object is the same object as this object, or if it is also a List and the sequence of elements returned by an List#iterator() over the specified list is the same as the sequence returned by an iterator over this list. The two sequences are considered to be the same if they have the same length and corresponding elements at the same position in the sequence are equal. Two elements e1 and e2 are considered equal if Objects.equals(e1, e2).

Parameters
obj the reference object with which to compare.
o the object to be compared for equality with this list
Return
Boolean true if the specified object is equal to this list

forEach

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

get

Added in API level 1
open fun get(index: Int): E

Returns the element at the specified position in this list.

Parameters
index Int: index of the element to return
Return
E the element at the specified position in this list
Exceptions
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

hashCode

Added in API level 1
open fun hashCode(): Int

Returns the hash code value for this list.

This implementation uses the definition in List#hashCode.

Return
Int the hash code value for this list

indexOf

Added in API level 1
open fun indexOf(
    e: E?,
    index: Int
): Int

Returns the index of the first occurrence of the specified element in this list, searching forwards from index, or returns -1 if the element is not found. More formally, returns the lowest index i such that i >= index && Objects.equals(get(i), e), or -1 if there is no such index.

Parameters
e E?: element to search for
index Int: index to start searching from
Return
Int the index of the first occurrence of the element in this list at position index or later in the list; -1 if the element is not found.
Exceptions
java.lang.IndexOutOfBoundsException if the specified index is negative

indexOf

Added in API level 1
open fun indexOf(element: E?): Int

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o element to search for
Return
Int the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

isEmpty

Added in API level 1
open fun isEmpty(): Boolean

Returns true if this list contains no elements.

Return
Boolean true if this list contains no elements

iterator

Added in API level 1
open fun iterator(): MutableIterator<E>

Returns an iterator over the elements in this list in proper sequence.

The returned iterator provides a snapshot of the state of the list when the iterator was constructed. No synchronization is needed while traversing the iterator. The iterator does NOT support the remove method.

Return
MutableIterator<E> an iterator over the elements in this list in proper sequence

lastIndexOf

Added in API level 1
open fun lastIndexOf(
    e: E?,
    index: Int
): Int

Returns the index of the last occurrence of the specified element in this list, searching backwards from index, or returns -1 if the element is not found. More formally, returns the highest index i such that i <= index && Objects.equals(get(i), e), or -1 if there is no such index.

Parameters
e E?: element to search for
index Int: index to start searching backwards from
Return
Int the index of the last occurrence of the element at position less than or equal to index in this list; -1 if the element is not found.
Exceptions
java.lang.IndexOutOfBoundsException if the specified index is greater than or equal to the current size of this list

lastIndexOf

Added in API level 1
open fun lastIndexOf(element: E?): Int

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the highest index i such that Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o element to search for
Return
Int the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

listIterator

Added in API level 1
open fun listIterator(): MutableListIterator<E>

Returns a list iterator over the elements in this list (in proper sequence).

The returned iterator provides a snapshot of the state of the list when the iterator was constructed. No synchronization is needed while traversing the iterator. The iterator does NOT support the remove, set or add methods.

Return
MutableListIterator<E> a list iterator over the elements in this list (in proper sequence)

listIterator

Added in API level 1
open fun listIterator(index: Int): MutableListIterator<E>

Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list. The specified index indicates the first element that would be returned by an initial call to ListIterator#next. An initial call to ListIterator#previous would return the element with the specified index minus one.

The returned iterator provides a snapshot of the state of the list when the iterator was constructed. No synchronization is needed while traversing the iterator. The iterator does NOT support the remove, set or add methods.

Parameters
index Int: index of the first element to be returned from the list iterator (by a call to ListIterator#next)
Return
MutableListIterator<E> a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list
Exceptions
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

remove

Added in API level 1
open fun remove(element: E?): Boolean

Removes the first occurrence of the specified element from this list, if it is present. If this list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that Objects.equals(o, get(i)) (if such an element exists). Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).

Parameters
o element to be removed from this list, if present
Return
Boolean true if this list contained the specified element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)
java.lang.UnsupportedOperationException if the remove operation is not supported by this list

removeAll

Added in API level 1
open fun removeAll(elements: Collection<E>): Boolean

Removes from this list all of its elements that are contained in the specified collection. This is a particularly expensive operation in this class because of the need for an internal temporary array.

Parameters
c collection containing elements to be removed from this list
Return
Boolean true if this list changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the removeAll operation is not supported by this list
java.lang.ClassCastException if the class of an element of this list is incompatible with the specified collection (optional)
java.lang.NullPointerException if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null

See Also

removeAt

Added in API level 1
open fun removeAt(index: Int): E

Removes the element at the specified position in this list. Shifts any subsequent elements to the left (subtracts one from their indices). Returns the element that was removed from the list.

Parameters
index Int: the index of the element to be removed
Return
E the element previously at the specified position
Exceptions
java.lang.UnsupportedOperationException if the remove operation is not supported by this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

removeIf

Added in API level 24
open fun removeIf(filter: Predicate<in E>): Boolean
Parameters
filter Predicate<in E>: a predicate which returns true for elements to be removed
Return
Boolean true if any elements were removed
Exceptions
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.

replaceAll

Added in API level 24
open fun replaceAll(operator: UnaryOperator<E>): Unit
Parameters
operator UnaryOperator<E>: the operator to apply to each element
Exceptions
java.lang.UnsupportedOperationException if this list is unmodifiable. Implementations may throw this exception if an element cannot be replaced or if, in general, modification is not supported
java.lang.NullPointerException if the specified operator is null or if the operator result is a null value and this list does not permit null elements (optional)

retainAll

Added in API level 1
open fun retainAll(elements: Collection<E>): Boolean

Retains only the elements in this list that are contained in the specified collection. In other words, removes from this list all of its elements that are not contained in the specified collection.

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

See Also

set

Added in API level 1
open fun set(
    index: Int,
    element: E
): E

Replaces the element at the specified position in this list with the specified element.

Parameters
index Int: index of the element to replace
element E: element to be stored at the specified position
Return
E the element previously at the specified position
Exceptions
java.lang.UnsupportedOperationException if the set operation is not supported by this list
java.lang.ClassCastException if the class of the specified element prevents it from being added to this list
java.lang.NullPointerException if the specified element is null and this list does not permit null elements
java.lang.IllegalArgumentException if some property of the specified element prevents it from being added to this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

sort

Added in API level 24
open fun sort(c: Comparator<in E>?): Unit
Parameters
c Comparator<in E>?: the Comparator used to compare list elements. A null value indicates that the elements' Comparable should be used
Exceptions
java.lang.ClassCastException if the list contains elements that are not mutually comparable using the specified comparator
java.lang.UnsupportedOperationException if the list's list-iterator does not support the set operation
java.lang.IllegalArgumentException (optional) if the comparator is found to violate the Comparator contract

spliterator

Added in API level 24
open fun spliterator(): Spliterator<E>

Returns a Spliterator over the elements in this list.

The Spliterator reports Spliterator#IMMUTABLE, Spliterator#ORDERED, Spliterator#SIZED, and Spliterator#SUBSIZED.

The spliterator provides a snapshot of the state of the list when the spliterator was constructed. No synchronization is needed while operating on the spliterator.

Return
Spliterator<E> a Spliterator over the elements in this list

subList

Added in API level 1
open fun subList(
    fromIndex: Int,
    toIndex: Int
): MutableList<E>

Returns a view of the portion of this list between fromIndex, inclusive, and toIndex, exclusive. The returned list is backed by this list, so changes in the returned list are reflected in this list.

The semantics of the list returned by this method become undefined if the backing list (i.e., this list) is modified in any way other than via the returned list.

Parameters
fromIndex Int: low endpoint (inclusive) of the subList
toIndex Int: high endpoint (exclusive) of the subList
Return
MutableList<E> a view of the specified range within this list
Exceptions
java.lang.IndexOutOfBoundsException for an illegal endpoint index value (fromIndex < 0 || toIndex > size || fromIndex > toIndex)

toArray

Added in API level 1
open fun toArray(): Array<Any!>

Returns an array containing all of the elements in this list in proper sequence (from first to last element).

The returned array will be "safe" in that no references to it are maintained by this list. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

Return
Array<Any!> an array containing all the elements in this list

toArray

Added in API level 1
open fun <T : Any!> toArray(a: Array<T>): Array<T>

Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list 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 list.

If this list fits in the specified array with room to spare (i.e., the array has more elements than this list), the element in the array immediately following the end of the list is set to null. (This is useful in determining the length of this list only if the caller knows that this list does not contain any null elements.)

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 list known to contain only strings. The following code can be used to dump the list into a newly allocated array of String:

<code>String[] y = x.toArray(new String[0]);</code>
Note that toArray(new Object[0]) is identical in function to toArray().
Parameters
<T> the runtime type of the array to contain the collection
a Array<T>: the array into which the elements of the list 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 list
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 list
java.lang.NullPointerException if the specified array is null

toString

Added in API level 1
open fun toString(): String

Returns a string representation of this list. The string representation consists of the string representations of the list'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 list

Properties

size

Added in API level 1
open val size: Int

Returns the number of elements in this list.

Return
Int the number of elements in this list