public class CopyOnWriteArrayList extends Object implements List, Cloneable, Serializable
This is ordinarily too costly, but it becomes attractive when traversal operations vastly overwhelm mutations, and, especially, when you cannot or don't want to synchronize traversals, yet need to preclude interference among concurrent threads. The 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. (The iterator will not traverse elements added or changed since the iterator was created, but usually this is a desirable feature.)
As much code and documentation as possible was shamelessly copied from java.util.ArrayList (Thanks, Josh!), with the intent of preserving all semantics of ArrayList except for the copy-on-write property. (The java.util collection code could not be subclassed here since all of the existing collection classes assume elementwise mutability.)
Because of the copy-on-write policy, some one-by-one mutative operations in the java.util.Arrays and java.util.Collections classes are so time/space intensive as to never be worth calling (except perhaps as benchmarks for garbage collectors :-).
Three methods are supported in addition to those described in List and ArrayList. The addIfAbsent and addAllAbsent methods provide Set semantics for add, and are used in CopyOnWriteArraySet. However, they can also be used directly from this List version. The copyIn method (and a constructor that invokes it) allow you to copy in an initial array to use. This method can be useful when you first want to perform many operations on a plain array, and then make a copy available for use through the collection API.
Due to their strict read-only nature, element-changing operations on iterators (remove, set, and add) are not supported. These are the only methods throwing UnsupportedOperationException.
CopyOnWriteArraySet,
Serialized Form| Modifier and Type | Class and Description |
|---|---|
protected static class |
CopyOnWriteArrayList.COWIterator |
protected static class |
CopyOnWriteArrayList.COWSubList |
| Modifier and Type | Field and Description |
|---|---|
protected Object[] |
array_
The held array.
|
| Constructor and Description |
|---|
CopyOnWriteArrayList()
Constructs an empty list
|
CopyOnWriteArrayList(Collection c)
Constructs an list containing the elements of the specified
Collection, in the order they are returned by the Collection's
iterator.
|
CopyOnWriteArrayList(Object[] toCopyIn)
Create a new CopyOnWriteArrayList holding a copy of given array
|
| Modifier and Type | Method and Description |
|---|---|
void |
add(int index,
Object element)
Inserts the specified element at the specified position in this
list.
|
boolean |
add(Object element)
Appends the specified element to the end of this list.
|
boolean |
addAll(Collection 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 c)
Inserts all of the elements in the specified Collection into this
list, starting at the specified position.
|
int |
addAllAbsent(Collection 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.
|
boolean |
addIfAbsent(Object element)
Append the element if not present.
|
protected Object[] |
array()
Accessor to the array intended to be called from
within unsynchronized read-only methods
|
void |
clear()
Removes all of the elements from this list.
|
Object |
clone()
Returns a shallow copy of this list.
|
boolean |
contains(Object elem)
Returns true if this list contains the specified element.
|
boolean |
containsAll(Collection c)
Returns true if this Collection contains all of the elements in the
specified Collection.
|
void |
copyIn(Object[] toCopyIn,
int first,
int n)
Replace the held array with a copy of the
n
elements of the provided array, starting at position first. |
boolean |
equals(Object o)
Compares the specified Object with this List for equality.
|
Object |
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 elem)
Searches for the first occurence of the given argument, testing
for equality using the
equals method. |
int |
indexOf(Object elem,
int index)
Searches for the first occurence of the given argument, beginning
the search at
index, and testing for equality using
the equals method. |
protected static int |
indexOf(Object elem,
Object[] elementData,
int len)
static version allows repeated call without needed
to grab lock for array each time
|
boolean |
isEmpty()
Tests if this list has no components.
|
Iterator |
iterator()
Returns an Iterator over the elements contained in this collection.
|
int |
lastIndexOf(Object elem)
Returns the index of the last occurrence of the specified object in
this list.
|
int |
lastIndexOf(Object elem,
int index)
Searches backwards for the specified object, starting from the
specified index, and returns an index to it.
|
protected static int |
lastIndexOf(Object elem,
Object[] elementData,
int len) |
ListIterator |
listIterator()
Returns an Iterator of the elements in this List (in proper sequence).
|
ListIterator |
listIterator(int index)
Returns a ListIterator of the elements in this List (in proper
sequence), starting at the specified position in the List.
|
protected void |
rangeCheck(int index,
int length)
Check if the given index is in range.
|
Object |
remove(int index)
Removes the element at the specified position in this list.
|
boolean |
remove(Object element)
Removes a single instance of the specified element from this Collection,
if it is present (optional operation).
|
boolean |
removeAll(Collection c)
Removes from this Collection all of its elements that are contained in
the specified Collection.
|
void |
removeRange(int fromIndex,
int toIndex)
Removes from this List all of the elements whose index is between
fromIndex, inclusive and toIndex, exclusive.
|
boolean |
retainAll(Collection c)
Retains only the elements in this Collection that are contained in the
specified Collection (optional operation).
|
Object |
set(int index,
Object element)
Replaces the element at the specified position in this list with
the specified element.
|
int |
size()
Returns the number of components in this list.
|
List |
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 the correct order.
|
Object[] |
toArray(Object[] a)
Returns an array containing all of the elements in this list in the
correct order.
|
String |
toString()
Returns a string representation of this Collection, containing
the String representation of each element.
|
protected transient Object[] array_
public CopyOnWriteArrayList()
public CopyOnWriteArrayList(Collection c)
public CopyOnWriteArrayList(Object[] toCopyIn)
toCopyIn - the array. A copy of this array is used as the
internal array.protected Object[] array()
public void copyIn(Object[] toCopyIn, int first, int n)
n
elements of the provided array, starting at position first.
To copy an entire array, call with arguments (array, 0, array.length).toCopyIn - the array. A copy of the indicated elements of
this array is used as the
internal array.first - The index of first position of the array to
start copying from.n - the number of elements to copy. This will be the new size of
the list.public int size()
size in interface Collectionsize in interface Listpublic boolean isEmpty()
isEmpty in interface CollectionisEmpty in interface Listtrue if this list has no components;
false otherwise.public boolean contains(Object elem)
contains in interface Collectioncontains in interface Listo - element whose presence in this List is to be tested.public int indexOf(Object elem)
equals method.indexOf in interface Listelem - an object.-1 if the object is not found.Object.equals(Object)protected static int indexOf(Object elem, Object[] elementData, int len)
public int indexOf(Object elem, int index)
index, and testing for equality using
the equals method.elem - an object.index - the index to start searching from.index or later in the
List; returns -1 if the object is not found.Object.equals(Object)public int lastIndexOf(Object elem)
lastIndexOf in interface Listelem - the desired component.public int lastIndexOf(Object elem, int index)
elem - the desired component.index - the index to start searching from.public Object clone()
public Object[] toArray()
toArray in interface CollectiontoArray in interface Listpublic Object[] toArray(Object[] 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 CollectiontoArray in interface Lista - 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 - the runtime type of a is not a supertype
of the runtime type of every element in this list.public Object get(int index)
get in interface Listindex - index of element to return.IndexOutOfBoundsException - index is out of range (index
< 0 || index >= size()).public Object set(int index, Object element)
set in interface Listindex - index of element to replace.element - element to be stored at the specified position.IndexOutOfBoundsException - index out of range
(index < 0 || index >= size()).public boolean add(Object element)
add in interface Collectionadd in interface Listelement - element to be appended to this list.public void add(int index,
Object element)
add in interface Listindex - index at which the specified element is to be inserted.element - element to be inserted.IndexOutOfBoundsException - index is out of range
(index < 0 || index > size()).public Object remove(int index)
remove in interface Listindex - the index of the element to removed.IndexOutOfBoundsException - index out of range (index
< 0 || index >= size()).public boolean remove(Object element)
e such that (o==null ? e==null :
o.equals(e)), if the Collection contains one or more such
elements. Returns true if the Collection contained the specified
element (or equivalently, if the Collection changed as a result of the
call).remove in interface Collectionremove in interface Listelement - element to be removed from this Collection, if present.public void removeRange(int fromIndex,
int toIndex)
fromIndex - index of first element to be removed.fromIndex - index after last element to be removed.IndexOutOfBoundsException - fromIndex or toIndex out of
range (fromIndex < 0 || fromIndex >= size() || toIndex
> size() || toIndex < fromIndex).public boolean addIfAbsent(Object element)
element - element to be added to this Collection, if absent.public boolean containsAll(Collection c)
This implementation iterates over the specified Collection, checking each element returned by the Iterator in turn to see if it's contained in this Collection. If all elements are so contained true is returned, otherwise false.
containsAll in interface CollectioncontainsAll in interface Listpublic boolean removeAll(Collection c)
removeAll in interface CollectionremoveAll in interface Listpublic boolean retainAll(Collection c)
retainAll in interface CollectionretainAll in interface Listpublic int addAllAbsent(Collection c)
c - elements to be added into this list.public void clear()
clear in interface Collectionclear in interface Listpublic boolean addAll(Collection c)
addAll in interface CollectionaddAll in interface Listc - elements to be inserted into this list.public boolean addAll(int index,
Collection c)
addAll in interface Listindex - index at which to insert first element
from the specified collection.c - elements to be inserted into this list.IndexOutOfBoundsException - index out of range (index
< 0 || index > size()).protected void rangeCheck(int index,
int length)
public String toString()
public boolean equals(Object o)
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.
This implementation first checks if the specified object is this List. If so, it returns true; if not, it checks if the specified object is a List. If not, it returns false; if so, it iterates over both lists, comparing corresponding pairs of elements. If any comparison returns false, this method returns false. If either Iterator runs out of elements before before the other it returns false (as the Lists are of unequal length); otherwise it returns true when the iterations complete.
public int hashCode()
This implementation uses exactly the code that is used to define the List hash function in the documentation for List.hashCode.
public Iterator iterator()
remove method.public ListIterator listIterator()
remove, set,
or add methods.listIterator in interface Listpublic ListIterator listIterator(int index)
listIterator in interface Listindex - index of first element to be returned from the
ListIterator (by a call to getNext).IndexOutOfBoundsException - index is out of range
(index < 0 || index > size()).public List subList(int fromIndex, int toIndex)
subList in interface ListfromIndex - low endpoint (inclusive) of the subList.toKey - high endpoint (exclusive) of the subList.IndexOutOfBoundsException - Illegal endpoint index value
(fromIndex < 0 || toIndex > size || fromIndex > toIndex).Copyright © 2012-2013 Adele Team | LIG. All Rights Reserved.