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java.lang.Object org.apache.wicket.util.concurrent.CopyOnWriteArrayList
public class CopyOnWriteArrayList
This class implements a variant of java.util.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 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.
[ Introduction to this package. ]
CopyOnWriteArraySet
,
Serialized FormNested Class Summary | |
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protected static class |
CopyOnWriteArrayList.COWIterator
|
protected static class |
CopyOnWriteArrayList.COWSubList
|
Field Summary | |
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protected java.lang.Object[] |
array_
The held array. |
Constructor Summary | |
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CopyOnWriteArrayList()
Constructs an empty list |
|
CopyOnWriteArrayList(java.util.Collection c)
Constructs an list containing the elements of the specified Collection, in the order they are returned by the Collection's iterator. |
|
CopyOnWriteArrayList(java.lang.Object[] toCopyIn)
Create a new CopyOnWriteArrayList holding a copy of given array |
Method Summary | |
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void |
add(int index,
java.lang.Object element)
Inserts the specified element at the specified position in this list. |
boolean |
add(java.lang.Object element)
Appends the specified element to the end of this list. |
boolean |
addAll(java.util.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,
java.util.Collection c)
Inserts all of the elements in the specified Collection into this list, starting at the specified position. |
int |
addAllAbsent(java.util.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(java.lang.Object element)
Append the element if not present. |
protected java.lang.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. |
java.lang.Object |
clone()
Returns a shallow copy of this list. |
boolean |
contains(java.lang.Object elem)
Returns true if this list contains the specified element. |
boolean |
containsAll(java.util.Collection c)
Returns true if this Collection contains all of the elements in the specified Collection. |
void |
copyIn(java.lang.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(java.lang.Object o)
Compares the specified Object with this List for equality. |
java.lang.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(java.lang.Object elem)
Searches for the first occurrence of the given argument, testing for equality using the equals method. |
int |
indexOf(java.lang.Object elem,
int index)
Searches for the first occurrence of the given argument, beginning the search at index , and testing for equality using the equals method. |
protected static int |
indexOf(java.lang.Object elem,
java.lang.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. |
java.util.Iterator |
iterator()
Returns an Iterator over the elements contained in this collection. |
int |
lastIndexOf(java.lang.Object elem)
Returns the index of the last occurrence of the specified object in this list. |
int |
lastIndexOf(java.lang.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(java.lang.Object elem,
java.lang.Object[] elementData,
int len)
|
java.util.ListIterator |
listIterator()
Returns an Iterator of the elements in this List (in proper sequence). |
java.util.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. |
java.lang.Object |
remove(int index)
Removes the element at the specified position in this list. |
boolean |
remove(java.lang.Object element)
Removes a single instance of the specified element from this Collection, if it is present (optional operation). |
boolean |
removeAll(java.util.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(java.util.Collection c)
Retains only the elements in this Collection that are contained in the specified Collection (optional operation). |
java.lang.Object |
set(int index,
java.lang.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. |
java.util.List |
subList(int fromIndex,
int toIndex)
Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive. |
java.lang.Object[] |
toArray()
Returns an array containing all of the elements in this list in the correct order. |
java.lang.Object[] |
toArray(java.lang.Object[] a)
Returns an array containing all of the elements in this list in the correct order. |
java.lang.String |
toString()
Returns a string representation of this Collection, containing the String representation of each element. |
Methods inherited from class java.lang.Object |
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finalize, getClass, notify, notifyAll, wait, wait, wait |
Field Detail |
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protected transient java.lang.Object[] array_
Constructor Detail |
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public CopyOnWriteArrayList()
public CopyOnWriteArrayList(java.util.Collection c)
c
- The collection to get the objects from.public CopyOnWriteArrayList(java.lang.Object[] toCopyIn)
toCopyIn
- the array. A copy of this array is used as the internal array.Method Detail |
---|
protected java.lang.Object[] array()
public void copyIn(java.lang.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 java.util.Collection
size
in interface java.util.List
public boolean isEmpty()
isEmpty
in interface java.util.Collection
isEmpty
in interface java.util.List
true
if this list has no components; false
otherwise.public boolean contains(java.lang.Object elem)
contains
in interface java.util.Collection
contains
in interface java.util.List
o
- element whose presence in this List is to be tested.public int indexOf(java.lang.Object elem)
equals
method.
indexOf
in interface java.util.List
elem
- an object.
-1
if the object is not found.Object.equals(Object)
protected static int indexOf(java.lang.Object elem, java.lang.Object[] elementData, int len)
elem
- elementData
- len
-
public int indexOf(java.lang.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(java.lang.Object elem)
lastIndexOf
in interface java.util.List
elem
- the desired component.
protected static int lastIndexOf(java.lang.Object elem, java.lang.Object[] elementData, int len)
public int lastIndexOf(java.lang.Object elem, int index)
elem
- the desired component.index
- the index to start searching from.
public java.lang.Object clone()
clone
in class java.lang.Object
public java.lang.Object[] toArray()
toArray
in interface java.util.Collection
toArray
in interface java.util.List
public java.lang.Object[] toArray(java.lang.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 java.util.Collection
toArray
in interface java.util.List
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.
java.lang.ArrayStoreException
- the runtime type of a is not a supertype of the runtime type of every element
in this list.public java.lang.Object get(int index)
get
in interface java.util.List
index
- index of element to return.
java.lang.IndexOutOfBoundsException
- index is out of range (index < 0 || index >= size()).public java.lang.Object set(int index, java.lang.Object element)
set
in interface java.util.List
index
- index of element to replace.element
- element to be stored at the specified position.
java.lang.IndexOutOfBoundsException
- index out of range (index < 0 || index >= size()).public boolean add(java.lang.Object element)
add
in interface java.util.Collection
add
in interface java.util.List
element
- element to be appended to this list.
public void add(int index, java.lang.Object element)
add
in interface java.util.List
index
- index at which the specified element is to be inserted.element
- element to be inserted.
java.lang.IndexOutOfBoundsException
- index is out of range (index < 0 || index > size()).public java.lang.Object remove(int index)
remove
in interface java.util.List
index
- the index of the element to removed.
java.lang.IndexOutOfBoundsException
- index out of range (index < 0 || index >= size()).public boolean remove(java.lang.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 java.util.Collection
remove
in interface java.util.List
element
- element to be removed from this Collection, if present.
public void removeRange(int fromIndex, int toIndex)
fromIndex
- index of first element to be removed.toIndex
- index after last element to be removed.
java.lang.IndexOutOfBoundsException
- fromIndex or toIndex out of range (fromIndex < 0 || fromIndex >= size() ||
toIndex > size() || toIndex < fromIndex).public boolean addIfAbsent(java.lang.Object element)
element
- element to be added to this Collection, if absent.
public boolean containsAll(java.util.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 java.util.Collection
containsAll
in interface java.util.List
public boolean removeAll(java.util.Collection c)
removeAll
in interface java.util.Collection
removeAll
in interface java.util.List
public boolean retainAll(java.util.Collection c)
retainAll
in interface java.util.Collection
retainAll
in interface java.util.List
public int addAllAbsent(java.util.Collection c)
c
- elements to be added into this list.
public void clear()
clear
in interface java.util.Collection
clear
in interface java.util.List
public boolean addAll(java.util.Collection c)
addAll
in interface java.util.Collection
addAll
in interface java.util.List
c
- elements to be inserted into this list.public boolean addAll(int index, java.util.Collection c)
addAll
in interface java.util.List
index
- index at which to insert first element from the specified collection.c
- elements to be inserted into this list.
java.lang.IndexOutOfBoundsException
- index out of range (index < 0 || index > size()).protected void rangeCheck(int index, int length)
index
- length
- public java.lang.String toString()
toString
in class java.lang.Object
public boolean equals(java.lang.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.
equals
in interface java.util.Collection
equals
in interface java.util.List
equals
in class java.lang.Object
o
- the Object to be compared for equality with this List.
public int hashCode()
This implementation uses exactly the code that is used to define the List hash function in the documentation for List.hashCode.
hashCode
in interface java.util.Collection
hashCode
in interface java.util.List
hashCode
in class java.lang.Object
public java.util.Iterator iterator()
remove
method.
iterator
in interface java.lang.Iterable
iterator
in interface java.util.Collection
iterator
in interface java.util.List
public java.util.ListIterator listIterator()
remove
, set
, or add
methods.
listIterator
in interface java.util.List
public java.util.ListIterator listIterator(int index)
listIterator
in interface java.util.List
index
- index of first element to be returned from the ListIterator (by a call to
getNext).
java.lang.IndexOutOfBoundsException
- index is out of range (index < 0 || index > size()).public java.util.List subList(int fromIndex, int toIndex)
subList
in interface java.util.List
fromIndex
- low endpoint (inclusive) of the subList.toKey
- high endpoint (exclusive) of the subList.
java.lang.IndexOutOfBoundsException
- Illegal endpoint index value (fromIndex < 0 || toIndex > size ||
fromIndex > toIndex).
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