|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object![]()
![]()
![]()
java.util.AbstractCollection
![]()
![]()
<E>
java.util.AbstractList
![]()
![]()
<E>
java.util.ArrayList<E>
public class 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 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.
Collection
List
LinkedList
Vector
Collections.synchronizedList(List)
Field Summary |
---|
Fields inherited from class java.util.AbstractList ![]() ![]() ![]() |
---|
modCount |
Constructor Summary | |
---|---|
ArrayList
Constructs an empty list with an initial capacity of ten. |
|
ArrayList
Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator. |
|
ArrayList
Constructs an empty list with the specified initial capacity. |
Method Summary | ||
---|---|---|
boolean |
add
Appends the specified element to the end of this list. |
|
void |
add
Inserts the specified element at the specified position in this list. |
|
boolean |
addAll
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
Inserts all of the elements in the specified Collection into this list, starting at the specified position. |
|
void |
clear
Removes all of the elements from this list. |
|
Object |
clone
Returns a shallow copy of this ArrayList instance. |
|
boolean |
contains
Returns true if this list contains the specified element. |
|
void |
ensureCapacity
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. |
|
E |
get
Returns the element at the specified position in this list. |
|
int |
indexOf
Searches for the first occurence of the given argument, testing for equality using the equals method. |
|
boolean |
isEmpty
Tests if this list has no elements. |
|
int |
lastIndexOf
Returns the index of the last occurrence of the specified object in this list. |
|
E |
remove
Removes the element at the specified position in this list. |
|
boolean |
remove
Removes a single instance of the specified element from this list, if it is present (optional operation). |
|
protected void |
removeRange
Removes from this List all of the elements whose index is between fromIndex, inclusive and toIndex, exclusive. |
|
E |
set
Replaces the element at the specified position in this list with the specified element. |
|
int |
size
Returns the number of elements in this list. |
|
Object |
toArray
Returns an array containing all of the elements in this list in the correct order. |
|
|
toArray
Returns an array containing all of the elements in this list in the correct order; 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. |
Methods inherited from class java.util.AbstractList ![]() ![]() ![]() |
---|
equals |
Methods inherited from class java.util.AbstractCollection ![]() ![]() ![]() |
---|
containsAll |
Methods inherited from class java.lang.Object ![]() ![]() ![]() |
---|
finalize |
Methods inherited from interface java.util.List ![]() ![]() ![]() |
---|
containsAll |
Constructor Detail |
---|
public ArrayList(int initialCapacity)
initialCapacity
- the initial capacity of the list.
IllegalArgumentException

- if the specified initial capacity
is negativepublic ArrayList()
public ArrayList(Collection![]()
![]()
<? extends E> c)
c
- the collection whose elements are to be placed into this list.
NullPointerException

- if the specified collection is null.Method Detail |
---|
public void trimToSize()
public void ensureCapacity(int minCapacity)
minCapacity
- the desired minimum capacity.public int size()
size

in interface Collection
<E>
size

in interface List
<E>
size

in class AbstractCollection
<E>
public boolean isEmpty()
isEmpty

in interface Collection
<E>
isEmpty

in interface List
<E>
isEmpty

in class AbstractCollection
<E>
public boolean contains(Object![]()
![]()
elem)
contains

in interface Collection
<E>
contains

in interface List
<E>
contains

in class AbstractCollection
<E>
elem
- element whose presence in this List is to be tested.
true
if the specified element is present;
false
otherwise.public int indexOf(Object![]()
![]()
elem)
indexOf

in interface List
<E>
indexOf

in class AbstractList
<E>
elem
- an object.
Object.equals(Object)
public int lastIndexOf(Object![]()
![]()
elem)
lastIndexOf

in interface List
<E>
lastIndexOf

in class AbstractList
<E>
elem
- the desired element.
public Object![]()
![]()
clone()
clone

in class Object

Cloneable
public Object![]()
![]()
[] toArray()
toArray

in interface Collection
<E>
toArray

in interface List
<E>
toArray

in class AbstractCollection
<E>
Arrays.asList(Object[])
public <T> T[] toArray(T[] a)
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.
toArray

in interface Collection
<E>
toArray

in interface List
<E>
toArray

in class AbstractCollection
<E>
a
- 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.
ArrayStoreException

- if the runtime type of a is not a supertype
of the runtime type of every element in this list.public E get(int index)
get

in interface List
<E>
get

in class AbstractList
<E>
index
- index of element to return.
IndexOutOfBoundsException

- if index is out of range (index
< 0 || index >= size()).public E set(int index, E element)
set

in interface List
<E>
set

in class AbstractList
<E>
index
- index of element to replace.element
- element to be stored at the specified position.
IndexOutOfBoundsException

- if index out of range
(index < 0 || index >= size()).public boolean add(E o)
add

in interface Collection
<E>
add

in interface List
<E>
add

in class AbstractList
<E>
o
- element to be appended to this list.
public void add(int index, E element)
add

in interface List
<E>
add

in class AbstractList
<E>
index
- index at which the specified element is to be inserted.element
- element to be inserted.
IndexOutOfBoundsException

- if index is out of range
(index < 0 || index > size()).public E remove(int index)
remove

in interface List
<E>
remove

in class AbstractList
<E>
index
- the index of the element to removed.
IndexOutOfBoundsException

- if index out of range (index
< 0 || index >= size()).public boolean remove(Object![]()
![]()
o)
remove

in interface Collection
<E>
remove

in interface List
<E>
remove

in class AbstractCollection
<E>
o
- element to be removed from this list, if present.
public void clear()
clear

in interface Collection
<E>
clear

in interface List
<E>
clear

in class AbstractList
<E>
public boolean addAll(Collection![]()
![]()
<? extends E> c)
addAll

in interface Collection
<E>
addAll

in interface List
<E>
addAll

in class AbstractCollection
<E>
c
- the elements to be inserted into this list.
NullPointerException

- if the specified collection is null.AbstractCollection.add(Object)
public boolean addAll(int index, Collection![]()
![]()
<? extends E> c)
addAll

in interface List
<E>
addAll

in class AbstractList
<E>
index
- index at which to insert first element
from the specified collection.c
- elements to be inserted into this list.
IndexOutOfBoundsException

- if index out of range (index
< 0 || index > size()).
NullPointerException

- if the specified Collection is null.protected void removeRange(int fromIndex, int toIndex)
removeRange

in class AbstractList
<E>
fromIndex
- index of first element to be removed.toIndex
- index after last element to be removed.
|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |