Package java.util

Class ArrayList<E>

java.lang.Object

java.util.ArrayList<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>, List<E>

public class ArrayList<E>
extends Object
implements List<E>

Constructor Summary

Constructors

Constructor	Description
ArrayList()	Constructs an empty list with an initial capacity of ten.
ArrayList(int initialCapacity)	Constructs an empty list with the specified initial capacity.

Method Summary

Modifier and Type	Method	Description
void	add(int index, E element)	Inserts the specified element at the specified position in this list.
boolean	add(E e)	Appends the specified element to the end of this list.
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.
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.
void	clear()	Removes all of the elements from this list.
boolean	contains(Object o)	Returns true if this list contains the specified element.
boolean	containsAll(Collection<?> arg0)	Tests whether this List contains all objects contained in the specified collection.
(package private) E	elementData(int index)
E	get(int index)	Returns the element at the specified position in 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.
(package private) int	indexOfRange(Object o, int start, int end)
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.
(package private) int	lastIndexOfRange(Object o, int start, int end)
ListIterator<E>	listIterator()	Returns a list iterator over the elements in this list (in proper sequence).
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.
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.
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.
List<E>	subList(int arg0, int arg1)	Returns a List of the specified portion of this List from the given start index to the end index minus one.
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[] arg0)	Returns an array containing all elements contained in this List.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, toString

Methods inherited from interface java.util.List

equals, hashCode

Constructor Detail

ArrayList

public ArrayList(int initialCapacity)

Constructs an empty list with the specified initial capacity.

Parameters:

initialCapacity - the initial capacity of the list

Throws:

IllegalArgumentException - if the specified initial capacity is negative

ArrayList

public ArrayList()

Constructs an empty list with an initial capacity of ten.

Method Detail

size

public int size()

Returns the number of elements in this list.

Specified by:

size in interface Collection<E>

Specified by:

size in interface List<E>

Returns:

the number of elements in this list

isEmpty

public boolean isEmpty()

Returns true if this list contains no elements.

Specified by:

isEmpty in interface Collection<E>

Specified by:

isEmpty in interface List<E>

Returns:

true if this list contains no elements

See Also:

List.size()

contains

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).

Specified by:

contains in interface Collection<E>

Specified by:

contains in interface List<E>

Parameters:

o - element whose presence in this list is to be tested

Returns:

true if this list contains the specified element

indexOf

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.

Specified by:

indexOf in interface List<E>

Parameters:

o - the object to search for.

Returns:

the index of the first occurrence of the object or -1 if the object was not found.

indexOfRange

int indexOfRange(Object o,
                 int start,
                 int end)

lastIndexOf

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.

Specified by:

lastIndexOf in interface List<E>

Parameters:

o - the object to search for.

Returns:

the index of the last occurrence of the object, or -1 if the object was not found.

lastIndexOfRange

int lastIndexOfRange(Object o,
                     int start,
                     int end)

get

public E get(int index)

Returns the element at the specified position in this list.

Specified by:

get in interface List<E>

Parameters:

index - index of the element to return

Returns:

the element at the specified position in this list

Throws:

IndexOutOfBoundsException - if location < 0 || location >= size()

set

public E set(int index,
             E element)

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

Specified by:

set in interface List<E>

Parameters:

index - index of the element to replace

element - element to be stored at the specified position

Returns:

the element previously at the specified position

Throws:

IndexOutOfBoundsException - if location < 0 || location >= size()

add

public boolean add(E e)

Appends the specified element to the end of this list.

Specified by:

add in interface Collection<E>

Specified by:

add in interface List<E>

Parameters:

e - element to be appended to this list

Returns:

true (as specified by Collection.add(E))

add

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).

Specified by:

add in interface List<E>

Parameters:

index - index at which the specified element is to be inserted

element - element to be inserted

Throws:

IndexOutOfBoundsException - if location < 0 || location > size()

addAll

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.)

Specified by:

addAll in interface Collection<E>

Specified by:

addAll in interface List<E>

Parameters:

c - collection containing elements to be added to this list

Returns:

true if this list changed as a result of the call

Throws:

NullPointerException - if the specified collection is null

addAll

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.

Specified by:

addAll in interface List<E>

Parameters:

index - index at which to insert the first element from the specified collection

c - collection containing elements to be added to this list

Returns:

true if this list changed as a result of the call

Throws:

IndexOutOfBoundsException - if location < 0 || location > size()

NullPointerException - if the specified collection is null

clear

public void clear()

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

Specified by:

clear in interface Collection<E>

Specified by:

clear in interface List<E>

See Also:

List.isEmpty(), List.size()

containsAll

public boolean containsAll(Collection<?> arg0)

Description copied from interface: List

Tests whether this List contains all objects contained in the specified collection.

Specified by:

containsAll in interface Collection<E>

Specified by:

containsAll in interface List<E>

Parameters:

arg0 - the collection of objects

Returns:

true if all objects in the specified collection are elements of this List, false otherwise.

remove

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).

Specified by:

remove in interface List<E>

Parameters:

index - the index of the element to be removed

Returns:

the element that was removed from the list

Throws:

IndexOutOfBoundsException - if location < 0 || location >= size()

remove

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 (o==null ? get(i)==null : o.equals(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).

Specified by:

remove in interface Collection<E>

Specified by:

remove in interface List<E>

Parameters:

o - element to be removed from this list, if present

Returns:

true if this list contained the specified element

removeAll

public boolean removeAll(Collection<?> c)

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

Specified by:

removeAll in interface Collection<E>

Specified by:

removeAll in interface List<E>

Parameters:

c - collection containing elements to be removed from this list

Returns:

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)

retainAll

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.

Specified by:

retainAll in interface Collection<E>

Specified by:

retainAll in interface List<E>

Parameters:

c - collection containing elements to be retained in this list

Returns:

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)

toArray

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.

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Returns:

an array containing all of the elements in this list in proper sequence

toArray

public <T> T[] toArray(T[] arg0)

Description copied from interface: List

Returns an array containing all elements contained in this List. If the specified array is large enough to hold the elements, the specified array is used, otherwise an array of the same type is created. If the specified array is used and is larger than this List, the array element following the collection elements is set to null.

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Type Parameters:

T - the type.

Parameters:

arg0 - the array.

Returns:

an array of the elements from this List.

subList

public List<E> subList(int arg0,
                       int arg1)

Description copied from interface: List

Returns a List of the specified portion of this List from the given start index to the end index minus one. The returned List is backed by this List so changes to it are reflected by the other.

Specified by:

subList in interface List<E>

Parameters:

arg0 - the index at which to start the sublist.

arg1 - the index one past the end of the sublist.

Returns:

a list of a portion of this List.

iterator

public Iterator<E> iterator()

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

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface List<E>

Returns:

an iterator over the elements in this list in proper sequence

See Also:

Iterator

listIterator

public ListIterator<E> listIterator()

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

The returned list iterator is fail-fast.

Specified by:

listIterator in interface List<E>

Returns:

a List iterator on the elements of this List

See Also:

listIterator(int)

listIterator

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.

Specified by:

listIterator in interface List<E>

Parameters:

index - the index at which to start the iteration.

Returns:

a list iterator on the elements of this List.

Throws:

IndexOutOfBoundsException - if location < 0 || location > size()

See Also:

ListIterator

elementData

E elementData(int index)