Added in API level 1

Summary: Inherited Fields | Ctors | Methods | Protected Methods | Inherited Methods

ArrayList

public class ArrayList
extends AbstractList<E> implements Cloneable, List<E>, RandomAccess, Serializable

java.lang.Object
↳	java.util.AbstractCollection<E>
	↳	java.util.AbstractList<E>
		↳	java.util.ArrayList<E>

Resizable-array implementation of the List interface. Implements all optional list operations, and permits all elements, including null. In addition to implementing the List interface, this class provides methods to manipulate the size of the array that is used internally to store the list. (This class is roughly equivalent to Vector, except that it is unsynchronized.)

The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. The add operation runs in amortized constant time, that is, adding n elements requires O(n) time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared to that for the LinkedList implementation.

Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at least as large as the list size. As elements are added to an ArrayList, its capacity grows automatically. The details of the growth policy are not specified beyond the fact that adding an element has constant amortized time cost.

An application can increase the capacity of an ArrayList instance before adding a large number of elements using the ensureCapacity operation. This may reduce the amount of incremental reallocation.

Note that this implementation is not synchronized. If multiple threads access an ArrayList instance concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements, or explicitly resizes the backing array; merely setting the value of an element is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

   List list = Collections.synchronizedList(new ArrayList(...));

The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

This class is a member of the Java Collections Framework.

See also:

Summary

Inherited fields

From class java.util.AbstractList


    protected
    
    
    int

modCount

The number of times this list has been structurally modified.

Public constructors
`ArrayList()` Constructs an empty list with an initial capacity of ten.
`ArrayList(int initialCapacity)` Constructs an empty list with the specified initial capacity.
`ArrayList(Collection<? extends E> c)` Constructs 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.
`void`	`addFirst(E element)` Adds an element as the first element of this collection (optional operation).
`void`	`addLast(E element)` 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 `ArrayList` instance.
`boolean`	`contains(Object o)` Returns `true` if this list contains the specified element.
`void`	`ensureCapacity(int minCapacity)` Increases the capacity of this `ArrayList` instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.
`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(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.
`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.
`ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this list (in proper sequence).
`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.
`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()` Creates a late-binding and fail-fast `Spliterator` over the elements in this list.
`List<E>`	`subList(int fromIndex, int toIndex)` Returns a view of the portion of this list between the specified `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.
`void`	`trimToSize()` Trims the capacity of this `ArrayList` instance to be the list's current size.

Protected methods
`void`	`removeRange(int fromIndex, int toIndex)` Removes from this list all of the elements whose index is between `fromIndex`, inclusive, and `toIndex`, exclusive.

Inherited methods

From class


        
          java.util.AbstractList

`void`	`add(int index, E element)` Inserts the specified element at the specified position in this list (optional operation).
`boolean`	`add(E e)` Appends the specified element to the end of this list (optional operation).
`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).
`void`	`clear()` Removes all of the elements from this list (optional operation).
`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.
`int`	`hashCode()` Returns the hash code value for this list.
`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.
`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.
`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.
`ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this list (in proper sequence).
`E`	`remove(int index)` Removes the element at the specified position in this list (optional operation).
`void`	`removeRange(int fromIndex, int toIndex)` Removes from this list all of the elements whose index is between `fromIndex`, inclusive, and `toIndex`, exclusive.
`E`	`set(int index, E element)` Replaces the element at the specified position in this list with the specified element (optional operation).
`List<E>`	`subList(int fromIndex, int toIndex)` Returns a view of the portion of this list between the specified `fromIndex`, inclusive, and `toIndex`, exclusive.

From class


        
          java.util.AbstractCollection

`boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`void`	`clear()` Removes all of the elements from this collection (optional operation).
`boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements contained in this collection.
`boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`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.
`<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.
`Object[]`	`toArray()` Returns an array containing all of the elements in this collection.
`String`	`toString()` Returns a string representation of this collection.

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

ArrayList

Added in API level 1

public ArrayList ()

Constructs an empty list with an initial capacity of ten.

ArrayList

Added in API level 1

public ArrayList (int initialCapacity)

Constructs an empty list with the specified initial capacity.

Parameters
`initialCapacity`	`int`: the initial capacity of the list

Throws
`IllegalArgumentException`	if the specified initial capacity is negative

ArrayList

Added in API level 1

public ArrayList (Collection<? extends E> c)

Constructs 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 whose elements are to be placed into this list

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. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this list, and this list is nonempty.)

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

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 the 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

addFirst

Added in API level 35

public void addFirst (E element)

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

addLast

Added in API level 35

public void addLast (E element)

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
`element`	`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 ArrayList instance. (The elements themselves are not copied.)

Returns
`Object`	a clone of this `ArrayList` instance

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

ensureCapacity

Added in API level 1

public void ensureCapacity (int minCapacity)

Increases the capacity of this ArrayList instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.

Parameters
`minCapacity`	`int`: the desired minimum capacity

equals

Added in API level 1

public boolean equals (Object o)

Compares the specified object with this list for equality. Returns true if and only if the specified object is also a list, both lists have the same size, and all corresponding pairs of elements in the two lists are equal. (Two elements e1 and e2 are equal if (e1==null ? e2==null : e1.equals(e2)).) In other words, two lists are defined to be equal if they contain the same elements in the same order.

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.

Returns
`int`	the hash code value for this list

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 is fail-fast.

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

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.

The returned list iterator is fail-fast.

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).

The returned list iterator is fail-fast.

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

See also:

listIterator(int)

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).

Parameters
`index`	`int`: the index of the element to be removed

Returns
`E`	the element that was removed from the list

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 the 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.

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:

Collection.contains(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:

Collection.contains(Object)

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 ()

Creates a late-binding and fail-fast Spliterator over the elements in this list.

The Spliterator reports Spliterator.SIZED, Spliterator.SUBSIZED, and Spliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values.

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 the specified fromIndex, inclusive, and toIndex, exclusive. (If fromIndex and toIndex are equal, the returned list is empty.) The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa. The returned list supports all of the optional list operations.

This method eliminates the need for explicit range operations (of the sort that commonly exist for arrays). Any operation that expects a list can be used as a range operation by passing a subList view instead of a whole list. For example, the following idiom removes a range of elements from a list:

      list.subList(from, to).clear();

Similar idioms may be constructed for indexOf(java.lang.Object) and lastIndexOf(java.lang.Object), and all of the algorithms in the Collections class can be applied to a subList.

The semantics of the list returned by this method become undefined if the backing list (i.e., this list) is structurally modified in any way other than via the returned list. (Structural modifications are those that change the size of this list, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.)

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`
`IllegalArgumentException`

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 of the elements in this list in proper sequence

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

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 the elements of the 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

trimToSize

Added in API level 1

public void trimToSize ()

Trims the capacity of this ArrayList instance to be the list's current size. An application can use this operation to minimize the storage of an ArrayList instance.

Protected methods

removeRange

Added in API level 1

protected void removeRange (int fromIndex, 
                int toIndex)

Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive. Shifts any succeeding elements to the left (reduces their index). This call shortens the list by (toIndex - fromIndex) elements. (If toIndex==fromIndex, this operation has no effect.)

Parameters
`fromIndex`	`int`: index of first element to be removed
`toIndex`	`int`: index after last element to be removed

Throws
`IndexOutOfBoundsException`	if `fromIndex` or `toIndex` is out of range (`fromIndex < 0 \|\| toIndex > size() \|\| toIndex < fromIndex`)