Added in API level 1

Summary: Ctors | Methods | Inherited Methods

CopyOnWriteArrayList

public class CopyOnWriteArrayList
extends Object implements Cloneable, List<E>, RandomAccess, Serializable

java.lang.Object
↳	java.util.concurrent.CopyOnWriteArrayList<E>

A thread-safe variant of 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.

This class is a member of the Java Collections Framework.

Summary

Public constructors
`CopyOnWriteArrayList()` Creates an empty list.
`CopyOnWriteArrayList(E[] toCopyIn)` Creates a list holding a copy of the given array.
`CopyOnWriteArrayList(Collection<? extends E> c)` Creates a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Public methods
`boolean`	`add(E e)` Appends the specified element to the end of this list.
`void`	`add(int index, E element)` Inserts the specified element at the specified position in this list.
`boolean`	`addAll(Collection<? extends E> c)` 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.
`boolean`	`addAll(int index, Collection<? extends E> c)` Inserts all of the elements in the specified collection into this list, starting at the specified position.
`int`	`addAllAbsent(Collection<? extends E> c)` 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.
`void`	`addFirst(E e)` Adds an element as the first element of this collection (optional operation).
`boolean`	`addIfAbsent(E e)` Appends the element, if not present.
`void`	`addLast(E e)` Adds an element as the last element of this collection (optional operation).
`void`	`clear()` Removes all of the elements from this list.
`Object`	`clone()` Returns a shallow copy of this list.
`boolean`	`contains(Object o)` Returns `true` if this list contains the specified element.
`boolean`	`containsAll(Collection<?> c)` Returns `true` if this list contains all of the elements of the specified collection.
`boolean`	`equals(Object o)` Compares the specified object with this list for equality.
`void`	`forEach(Consumer<? super E> action)`
`E`	`get(int index)` Returns the element at the specified position in this list.
`E`	`getFirst()` Gets the first element of this collection.
`E`	`getLast()` Gets the last element of this collection.
`int`	`hashCode()` Returns the hash code value for this list.
`int`	`indexOf(E e, int index)` 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.
`int`	`indexOf(Object o)` Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
`boolean`	`isEmpty()` Returns `true` if this list contains no elements.
`Iterator<E>`	`iterator()` Returns an iterator over the elements in this list in proper sequence.
`int`	`lastIndexOf(Object o)` Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
`int`	`lastIndexOf(E e, int index)` 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.
`ListIterator<E>`	`listIterator(int index)` Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list. The returned iterator provides a snapshot of the state of the list when the iterator was constructed.
`ListIterator<E>`	`listIterator()` 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.
`E`	`remove(int index)` Removes the element at the specified position in this list.
`boolean`	`remove(Object o)` Removes the first occurrence of the specified element from this list, if it is present.
`boolean`	`removeAll(Collection<?> c)` Removes from this list all of its elements that are contained in the specified collection.
`E`	`removeFirst()` Removes and returns the first element of this collection (optional operation).
`boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`E`	`removeLast()` Removes and returns the last element of this collection (optional operation).
`void`	`replaceAll(UnaryOperator<E> operator)` Replaces each element of this list with the result of applying the operator to that element.
`boolean`	`retainAll(Collection<?> c)` Retains only the elements in this list that are contained in the specified collection.
`List<E>`	`reversed()` Returns a reverse-ordered view of this collection. Modifications to the reversed view are permitted and will be propagated to this list.
`E`	`set(int index, E element)` Replaces the element at the specified position in this list with the specified element.
`int`	`size()` Returns the number of elements in this list.
`void`	`sort(Comparator<? super E> c)` Sorts this list according to the order induced by the specified `Comparator`.
`Spliterator<E>`	`spliterator()` Returns a `Spliterator` over the elements in this list.
`List<E>`	`subList(int fromIndex, int toIndex)` Returns a view of the portion of this list between `fromIndex`, inclusive, and `toIndex`, exclusive.
`Object[]`	`toArray()` Returns an array containing all of the elements in this list in proper sequence (from first to last element).
`<T> T[]`	`toArray(T[] a)` 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.
`String`	`toString()` Returns a string representation of this list.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.util.List

`abstract boolean`	`add(E e)` Appends the specified element to the end of this list (optional operation).
`abstract void`	`add(int index, E element)` Inserts the specified element at the specified position in this list (optional operation).
`abstract boolean`	`addAll(Collection<? extends E> c)` 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 (optional operation).
`abstract boolean`	`addAll(int index, Collection<? extends E> c)` Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
`default void`	`addFirst(E e)` Adds an element as the first element of this collection (optional operation).
`default void`	`addLast(E e)` Adds an element as the last element of this collection (optional operation).
`abstract void`	`clear()` Removes all of the elements from this list (optional operation).
`abstract boolean`	`contains(Object o)` Returns `true` if this list contains the specified element.
`abstract boolean`	`containsAll(Collection<?> c)` Returns `true` if this list contains all of the elements of the specified collection.
`static <E> List<E>`	`copyOf(Collection<? extends E> coll)` Returns an unmodifiable List containing the elements of the given Collection, in its iteration order.
`abstract boolean`	`equals(Object o)` Compares the specified object with this list for equality.
`abstract E`	`get(int index)` Returns the element at the specified position in this list.
`default E`	`getFirst()` Gets the first element of this collection.
`default E`	`getLast()` Gets the last element of this collection.
`abstract int`	`hashCode()` Returns the hash code value for this list.
`abstract int`	`indexOf(Object o)` Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
`abstract boolean`	`isEmpty()` Returns `true` if this list contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this list in proper sequence.
`abstract int`	`lastIndexOf(Object o)` Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
`abstract ListIterator<E>`	`listIterator(int index)` Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
`abstract ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this list (in proper sequence).
`static <E> List<E>`	`of(E e1, E e2, E e3)` Returns an unmodifiable list containing three elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)` Returns an unmodifiable list containing nine elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4, E e5)` Returns an unmodifiable list containing five elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6)` Returns an unmodifiable list containing six elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)` Returns an unmodifiable list containing eight elements.
`static <E> List<E>`	`of(E... elements)` Returns an unmodifiable list containing an arbitrary number of elements.
`static <E> List<E>`	`of()` Returns an unmodifiable list containing zero elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10)` Returns an unmodifiable list containing ten elements.
`static <E> List<E>`	`of(E e1, E e2)` Returns an unmodifiable list containing two elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)` Returns an unmodifiable list containing seven elements.
`static <E> List<E>`	`of(E e1, E e2, E e3, E e4)` Returns an unmodifiable list containing four elements.
`static <E> List<E>`	`of(E e1)` Returns an unmodifiable list containing one element.
`abstract E`	`remove(int index)` Removes the element at the specified position in this list (optional operation).
`abstract boolean`	`remove(Object o)` Removes the first occurrence of the specified element from this list, if it is present (optional operation).
`abstract boolean`	`removeAll(Collection<?> c)` Removes from this list all of its elements that are contained in the specified collection (optional operation).
`default E`	`removeFirst()` Removes and returns the first element of this collection (optional operation).
`default E`	`removeLast()` Removes and returns the last element of this collection (optional operation).
`default void`	`replaceAll(UnaryOperator<E> operator)` Replaces each element of this list with the result of applying the operator to that element.
`abstract boolean`	`retainAll(Collection<?> c)` Retains only the elements in this list that are contained in the specified collection (optional operation).
`default List<E>`	`reversed()` Returns a reverse-ordered view of this collection.
`abstract E`	`set(int index, E element)` Replaces the element at the specified position in this list with the specified element (optional operation).
`abstract int`	`size()` Returns the number of elements in this list.
`default void`	`sort(Comparator<? super E> c)` Sorts this list according to the order induced by the specified `Comparator`.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this list.
`abstract List<E>`	`subList(int fromIndex, int toIndex)` Returns a view of the portion of this list between the specified `fromIndex`, inclusive, and `toIndex`, exclusive.
`abstract Object[]`	`toArray()` Returns an array containing all of the elements in this list in proper sequence (from first to last element).
`abstract <T> T[]`	`toArray(T[] a)` 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.

From interface


        
          java.util.Collection

`abstract boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`abstract boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`abstract void`	`clear()` Removes all of the elements from this collection (optional operation).
`abstract boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`abstract boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`abstract boolean`	`equals(Object o)` Compares the specified object with this collection for equality.
`abstract int`	`hashCode()` Returns the hash code value for this collection.
`abstract boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this collection.
`default Stream<E>`	`parallelStream()` Returns a possibly parallel `Stream` with this collection as its source.
`abstract boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`abstract boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`default boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`abstract boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`abstract int`	`size()` Returns the number of elements in this collection.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this collection.
`default Stream<E>`	`stream()` Returns a sequential `Stream` with this collection as its source.
`abstract <T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
`abstract Object[]`	`toArray()` Returns an array containing all of the elements in this collection.
`default <T> T[]`	`toArray(IntFunction<T[]> generator)` Returns an array containing all of the elements in this collection, using the provided `generator` function to allocate the returned array.

From interface


        
          java.util.SequencedCollection

`default void`	`addFirst(E e)` Adds an element as the first element of this collection (optional operation).
`default void`	`addLast(E e)` Adds an element as the last element of this collection (optional operation).
`default E`	`getFirst()` Gets the first element of this collection.
`default E`	`getLast()` Gets the last element of this collection.
`default E`	`removeFirst()` Removes and returns the first element of this collection (optional operation).
`default E`	`removeLast()` Removes and returns the last element of this collection (optional operation).
`abstract SequencedCollection<E>`	`reversed()` Returns a reverse-ordered view of this collection.

From interface


        
          java.lang.Iterable

`default void`	`forEach(Consumer<? super T> action)` Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception.
`abstract Iterator<E>`	`iterator()` Returns an iterator over elements of type `T`.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements described by this `Iterable`.

Public constructors

CopyOnWriteArrayList

Added in API level 1

public CopyOnWriteArrayList ()

Creates an empty list.

CopyOnWriteArrayList

Added in API level 1

public CopyOnWriteArrayList (E[] toCopyIn)

Creates a list holding a copy of the given array.

Parameters
`toCopyIn`	`E`: the array (a copy of this array is used as the internal array)

Throws
`NullPointerException`	if the specified array is null

CopyOnWriteArrayList

Added in API level 1

public CopyOnWriteArrayList (Collection<? extends E> c)

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

Parameters
`c`	`Collection`: the collection of initially held elements

Throws
`NullPointerException`	if the specified collection is null

Public methods

add

Added in API level 1

public boolean add (E e)

Appends the specified element to the end of this list.

Parameters
`e`	`E`: element to be appended to this list

Returns
`boolean`	`true` (as specified by `Collection.add`)

add

Added in API level 1

public void add (int index, 
                E element)

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

Throws
`IndexOutOfBoundsException`

addAll

Added in API level 1

public boolean addAll (Collection<? extends E> c)

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`: collection containing elements to be added to this list

Returns
`boolean`	`true` if this list changed as a result of the call

Throws
`NullPointerException`	if the specified collection is null

See also:

add(Object)

addAll

Added in API level 1

public boolean addAll (int index, 
                Collection<? extends E> c)

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`: collection containing elements to be added to this list

Returns
`boolean`	`true` if this list changed as a result of the call

Throws
`IndexOutOfBoundsException`
`NullPointerException`	if the specified collection is null

See also:

add(int, Object)

addAllAbsent

Added in API level 1

public int addAllAbsent (Collection<? extends E> c)

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`	`Collection`: collection containing elements to be added to this list

Returns
`int`	the number of elements added

Throws
`NullPointerException`	if the specified collection is null

See also:

addIfAbsent(Object)

addFirst

Added in API level 35

public void addFirst (E e)

Adds an element as the first element of this collection (optional operation). After this operation completes normally, the given element will be a member of this collection, and it will be the first element in encounter order.

Parameters
`e`	`E`: the element to be added

addIfAbsent

Added in API level 1

public boolean addIfAbsent (E e)

Appends the element, if not present.

Parameters
`e`	`E`: element to be added to this list, if absent

Returns
`boolean`	`true` if the element was added

addLast

Added in API level 35

public void addLast (E e)

Adds an element as the last element of this collection (optional operation). After this operation completes normally, the given element will be a member of this collection, and it will be the last element in encounter order.

Parameters
`e`	`E`: the element to be added.

clear

Added in API level 1

public void clear ()

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

clone

Added in API level 1

public Object clone ()

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

Returns
`Object`	a clone of this list

contains

Added in API level 1

public boolean contains (Object o)

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`	`Object`: element whose presence in this list is to be tested

Returns
`boolean`	`true` if this list contains the specified element

containsAll

Added in API level 1

public boolean containsAll (Collection<?> c)

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

Parameters
`c`	`Collection`: collection to be checked for containment in this list

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

Throws
`NullPointerException`	if the specified collection is null

See also:

contains(Object)

equals

Added in API level 1

public boolean equals (Object o)

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 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
`o`	`Object`: the object to be compared for equality with this list

Returns
`boolean`	`true` if the specified object is equal to this list

forEach

Added in API level 24

public void forEach (Consumer<? super E> action)

Parameters
`action`	`Consumer`

Throws
`NullPointerException`

get

Added in API level 1

public E get (int index)

Returns the element at the specified position in this list.

Parameters
`index`	`int`: index of the element to return

Returns
`E`	the element at the specified position in this list

Throws
`IndexOutOfBoundsException`

getFirst

Added in API level 35

public E getFirst ()

Gets the first element of this collection.

Returns
`E`	the retrieved element

Throws
`NoSuchElementException`

getLast

Added in API level 35

public E getLast ()

Gets the last element of this collection.

Returns
`E`	the retrieved element

Throws
`NoSuchElementException`

hashCode

Added in API level 1

public int hashCode ()

Returns the hash code value for this list.

This implementation uses the definition in List.hashCode.

Returns
`int`	the hash code value for this list

indexOf

Added in API level 1

public int indexOf (E e, 
                int index)

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

Returns
`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.

Throws
`IndexOutOfBoundsException`	if the specified index is negative

indexOf

Added in API level 1

public int indexOf (Object o)

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`	`Object`: element to search for

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

isEmpty

Added in API level 1

public boolean isEmpty ()

Returns true if this list contains no elements.

Returns
`boolean`	`true` if this list contains no elements

iterator

Added in API level 1

public Iterator<E> iterator ()

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.

Returns
`Iterator<E>`	an iterator over the elements in this list in proper sequence

lastIndexOf

Added in API level 1

public int lastIndexOf (Object o)

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`	`Object`: element to search for

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

lastIndexOf

Added in API level 1

public int lastIndexOf (E e, 
                int index)

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

Returns
`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.

Throws
`IndexOutOfBoundsException`	if the specified index is greater than or equal to the current size of this list

listIterator

Added in API level 1

public ListIterator<E> listIterator (int index)

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 next. An initial call to previous would return the element with the specified index minus one.

Parameters
`index`	`int`: index of the first element to be returned from the list iterator (by a call to `next`)

Returns
`ListIterator<E>`	a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list

Throws
`IndexOutOfBoundsException`

listIterator

Added in API level 1

public ListIterator<E> listIterator ()

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

Returns
`ListIterator<E>`	a list iterator over the elements in this list (in proper sequence)

remove

Added in API level 1

public E remove (int index)

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

Returns
`E`	the element previously at the specified position

Throws
`IndexOutOfBoundsException`

remove

Added in API level 1

public boolean remove (Object o)

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`	`Object`: element to be removed from this list, if present

Returns
`boolean`	`true` if this list contained the specified element

removeAll

Added in API level 1

public boolean removeAll (Collection<?> c)

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`: collection containing elements to be removed from this list

Returns
`boolean`	`true` if this list changed as a result of the call

Throws
`ClassCastException`	if the class of an element of this list is incompatible with the specified collection (optional)
`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:

remove(Object)

removeFirst

Added in API level 35

public E removeFirst ()

Removes and returns the first element of this collection (optional operation).

Returns
`E`	the removed element

Throws
`NoSuchElementException`

removeIf

Added in API level 24

public boolean removeIf (Predicate<? super E> filter)

Removes all of the elements of this collection that satisfy the given predicate. Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller.

Parameters
`filter`	`Predicate`: a predicate which returns `true` for elements to be removed

Returns
`boolean`	`true` if any elements were removed

Throws
`NullPointerException`

removeLast

Added in API level 35

public E removeLast ()

Removes and returns the last element of this collection (optional operation).

Returns
`E`	the removed element

Throws
`NoSuchElementException`

replaceAll

Added in API level 24

public void replaceAll (UnaryOperator<E> operator)

Replaces each element of this list with the result of applying the operator to that element. Errors or runtime exceptions thrown by the operator are relayed to the caller.

Parameters
`operator`	`UnaryOperator`: the operator to apply to each element

retainAll

Added in API level 1

public boolean retainAll (Collection<?> c)

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`: collection containing elements to be retained in this list

Returns
`boolean`	`true` if this list changed as a result of the call

Throws
`ClassCastException`	if the class of an element of this list is incompatible with the specified collection (optional)
`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:

remove(Object)

reversed

Added in API level 35

public List<E> reversed ()

Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.

Modifications to the reversed view are permitted and will be propagated to this list. In addition, modifications to this list will be visible in the reversed view. Sublists and iterators of the reversed view have the same restrictions as those of this list.

Returns
`List<E>`	a reverse-ordered view of this collection, as a `List`

set

Added in API level 1

public E set (int index, 
                E element)

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

Returns
`E`	the element previously at the specified position

Throws
`IndexOutOfBoundsException`

size

Added in API level 1

public int size ()

Returns the number of elements in this list.

Returns
`int`	the number of elements in this list

sort

Added in API level 24

public void sort (Comparator<? super E> c)

Sorts this list according to the order induced by the specified Comparator.

All elements in this list must be mutually comparable using the specified comparator (that is, c.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the list).

If the specified comparator is null then all elements in this list must implement the Comparable interface and the elements' natural ordering should be used.

This list must be modifiable, but need not be resizable.

For apps running on and targeting Android versions greater than Nougat (API level > 25), Collections.sort(List) delegates to this method. Such apps must not call Collections.sort(List) from this method. Instead, prefer not overriding this method at all. If you must override it, consider this implementation:

 @Override
 public void sort(Comparator<? super E> c) {
   Object[] elements = toArray();
   Arrays.sort(elements, c);
   ListIterator<E> iterator = (ListIterator<Object>) listIterator();
   for (Object element : elements) {
     iterator.next();
     iterator.set((E) element);
   }
 }

Parameters
`c`	`Comparator`: the `Comparator` used to compare list elements. A `null` value indicates that the elements' natural ordering should be used

spliterator

Added in API level 24

public Spliterator<E> spliterator ()

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.

Returns
`Spliterator<E>`	a `Spliterator` over the elements in this list

subList

Added in API level 1

public List<E> subList (int fromIndex, 
                int toIndex)

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

Returns
`List<E>`	a view of the specified range within this list

Throws
`IndexOutOfBoundsException`

toArray

Added in API level 1

public Object[] toArray ()

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.

Returns
`Object[]`	an array containing all the elements in this list

toArray

Added in API level 1

public T[] toArray (T[] a)

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:

 String[] y = x.toArray(new String[0]);

Note that toArray(new Object[0]) is identical in function to toArray().

Parameters
`a`	`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.

Returns
`T[]`	an array containing all the elements in this list

Throws
`ArrayStoreException`	if the runtime type of the specified array is not a supertype of the runtime type of every element in this list
`NullPointerException`	if the specified array is null

toString

Added in API level 1

public String toString ()

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).

Returns
`String`	a string representation of this list