| java.lang.Object
 wicket.util.concurrent.CopyOnWriteArrayList
| CopyOnWriteArrayList | | public class CopyOnWriteArrayList implements List,Cloneable,java.io.Serializable(Code) | | 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. ]
See Also: CopyOnWriteArraySet |
| Inner Class :protected static class COWIterator implements ListIterator | |
| Inner Class :protected static class COWSubList extends AbstractList | |
| Field Summary | |
| protected transient Object[] | array_
The held array. |
| Constructor Summary | |
| public | CopyOnWriteArrayList()
| | public | CopyOnWriteArrayList(Collection c)
Constructs an list containing the elements of the specified Collection,
in the order they are returned by the Collection's iterator.
Parameters:
c - The collection to get the objects from. | | public | CopyOnWriteArrayList(Object[] toCopyIn)
Create a new CopyOnWriteArrayList holding a copy of given array
Parameters:
toCopyIn - the array. |
| Method Summary | |
| public synchronized boolean | add(Object element)
Appends the specified element to the end of this list.
Parameters:
element - element to be appended to this list. | | public synchronized void | add(int index, Object element)
Inserts the specified element at the specified position in this list. | | public synchronized 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. | | public synchronized boolean | addAll(int index, Collection c)
Inserts all of the elements in the specified Collection into this list,
starting at the specified position. | | public synchronized 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.
Parameters:
c - elements to be added into this list. | | public synchronized boolean | addIfAbsent(Object element)
Append the element if not present. | | protected synchronized Object[] | array()
| | public synchronized void | clear()
Removes all of the elements from this list. | | public Object | clone()
Returns a shallow copy of this list. | | public boolean | contains(Object elem)
Returns true if this list contains the specified element. | | public boolean | containsAll(Collection c)
Returns true if this Collection contains all of the elements in the
specified Collection.
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. | | public synchronized 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. | | public boolean | equals(Object o)
Compares the specified Object with this List for equality. | | public Object | get(int index)
Returns the element at the specified position in this list. | | public int | hashCode()
Returns the hash code value for this List. | | public int | indexOf(Object elem)
Searches for the first occurence of the given argument, testing for
equality using the equals method.
Parameters:
elem - an object. | | protected static int | indexOf(Object elem, Object[] elementData, int len)
static version allows repeated call without needed to grab lock for array
each time
Parameters:
elem -
Parameters:
elementData -
Parameters:
len - The index that is found. | | public 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.
Parameters:
elem - an object.
Parameters:
index - the index to start searching from. | | public boolean | isEmpty()
Tests if this list has no components. | | public Iterator | iterator()
Returns an Iterator over the elements contained in this collection. | | public int | lastIndexOf(Object elem)
Returns the index of the last occurrence of the specified object in this
list.
Parameters:
elem - the desired component. | | protected static int | lastIndexOf(Object elem, Object[] elementData, int len)
| | public int | lastIndexOf(Object elem, int index)
Searches backwards for the specified object, starting from the specified
index, and returns an index to it.
Parameters:
elem - the desired component.
Parameters:
index - the index to start searching from. | | public ListIterator | listIterator()
Returns an Iterator of the elements in this List (in proper sequence).
The iterator provides a snapshot of the state of the list when the
iterator was constructed. | | public 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. | | public synchronized Object | remove(int index)
Removes the element at the specified position in this list. | | public synchronized boolean | remove(Object element)
Removes a single instance of the specified element from this Collection,
if it is present (optional operation). | | public synchronized boolean | removeAll(Collection c)
Removes from this Collection all of its elements that are contained in
the specified Collection. | | public synchronized void | removeRange(int fromIndex, int toIndex)
Removes from this List all of the elements whose index is between
fromIndex, inclusive and toIndex, exclusive. | | public synchronized boolean | retainAll(Collection c)
Retains only the elements in this Collection that are contained in the
specified Collection (optional operation). | | public synchronized Object | set(int index, Object element)
Replaces the element at the specified position in this list with the
specified element.
Parameters:
index - index of element to replace.
Parameters:
element - element to be stored at the specified position. | | public int | size()
Returns the number of components in this list. | | public synchronized List | subList(int fromIndex, int toIndex)
Returns a view of the portion of this List between fromIndex, inclusive,
and toIndex, exclusive. | | public Object[] | toArray()
Returns an array containing all of the elements in this list in the
correct order. | | public Object[] | toArray(Object a)
Returns an array containing all of the elements in this list in the
correct order. | | public String | toString()
Returns a string representation of this Collection, containing the String
representation of each element. |
| array_ | | protected transient Object[] array_(Code) | | The held array. Directly access only within synchronized methods
|
| CopyOnWriteArrayList | | public CopyOnWriteArrayList()(Code) | | Constructs an empty list
|
| CopyOnWriteArrayList | | public CopyOnWriteArrayList(Collection c)(Code) | | Constructs an list containing the elements of the specified Collection,
in the order they are returned by the Collection's iterator.
Parameters:
c - The collection to get the objects from. |
| CopyOnWriteArrayList | | public CopyOnWriteArrayList(Object[] toCopyIn)(Code) | | Create a new CopyOnWriteArrayList holding a copy of given array
Parameters:
toCopyIn - the array. A copy of this array is used as the internal array. |
| add | | public synchronized boolean add(Object element)(Code) | | Appends the specified element to the end of this list.
Parameters:
element - element to be appended to this list. true (as per the general contract of Collection.add). |
| add | | public synchronized void add(int index, Object element)(Code) | | 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 - index at which the specified element is to be inserted.
Parameters:
element - element to be inserted.
exception:
IndexOutOfBoundsException - index is out of range (index < 0 || index > size()). |
| addAll | | public synchronized boolean addAll(Collection c)(Code) | | 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.
Parameters:
c - elements to be inserted into this list. |
| addAll | | public synchronized boolean addAll(int index, Collection c)(Code) | | 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 - index at which to insert first element from the specifiedcollection.
Parameters:
c - elements to be inserted into this list.
exception:
IndexOutOfBoundsException - index out of range (index < 0 || index > size()). |
| addAllAbsent | | public synchronized int addAllAbsent(Collection c)(Code) | | 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.
Parameters:
c - elements to be added into this list. the number of elements added |
| addIfAbsent | | public synchronized boolean addIfAbsent(Object element)(Code) | | Append the element if not present. This operation can be used to obtain
Set semantics for lists.
Parameters:
element - element to be added to this Collection, if absent. true if added |
| array | | protected synchronized Object[] array()(Code) | | Accessor to the array intended to be called from within unsynchronized
read-only methods
The internal array |
| clear | | public synchronized void clear()(Code) | | Removes all of the elements from this list.
|
| clone | | public Object clone()(Code) | | Returns a shallow copy of this list. (The elements themselves are not
copied.)
a clone of this list. |
| contains | | public boolean contains(Object elem)(Code) | | Returns true if this list contains the specified element.
Parameters:
o - element whose presence in this List is to be tested. |
| containsAll | | public boolean containsAll(Collection c)(Code) | | Returns true if this Collection contains all of the elements in the
specified Collection.
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.
|
| copyIn | | public synchronized void copyIn(Object[] toCopyIn, int first, int n)(Code) | | Replace the held array with a copy of the n elements of
the provided array, starting at position first. To copy
an entire array, call with arguments (array, 0, array.length).
Parameters:
toCopyIn - the array. A copy of the indicated elements of this array isused as the internal array.
Parameters:
first - The index of first position of the array to start copyingfrom.
Parameters:
n - the number of elements to copy. This will be the new size ofthe list. |
| equals | | public boolean equals(Object o)(Code) | | 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.
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.
Parameters:
o - the Object to be compared for equality with this List. true if the specified Object is equal to this List. |
| get | | public Object get(int index)(Code) | | Returns the element at the specified position in this list.
Parameters:
index - index of element to return.
exception:
IndexOutOfBoundsException - index is out of range (index < 0 || index >=size()). |
| hashCode | | public int hashCode()(Code) | | Returns the hash code value for this List.
This implementation uses exactly the code that is used to define the List
hash function in the documentation for List.hashCode.
|
| indexOf | | public int indexOf(Object elem)(Code) | | Searches for the first occurence of the given argument, testing for
equality using the equals method.
Parameters:
elem - an object. the index of the first occurrence of the argument in this list;returns -1 if the object is not found.
See Also: Object.equals(Object) |
| indexOf | | protected static int indexOf(Object elem, Object[] elementData, int len)(Code) | | static version allows repeated call without needed to grab lock for array
each time
Parameters:
elem -
Parameters:
elementData -
Parameters:
len - The index that is found. -1 if not found |
| indexOf | | public int indexOf(Object elem, int index)(Code) | | Searches for the first occurence of the given argument, beginning the
search at index, and testing for equality using the
equals method.
Parameters:
elem - an object.
Parameters:
index - the index to start searching from. the index of the first occurrence of the object argument in thisList at position index or later in the List;returns -1 if the object is not found.
See Also: Object.equals(Object) |
| isEmpty | | public boolean isEmpty()(Code) | | Tests if this list has no components.
true if this list has no components;false otherwise. |
| iterator | | public Iterator iterator()(Code) | | Returns an Iterator over the elements contained in this collection. The
iterator provides a snapshot of the state of the list when the iterator
was constructed. No synchronization is needed while traversing the
iterator. The iterator does NOT support the
remove method.
|
| lastIndexOf | | public int lastIndexOf(Object elem)(Code) | | Returns the index of the last occurrence of the specified object in this
list.
Parameters:
elem - the desired component. the index of the last occurrence of the specified object in thislist; returns -1 if the object is not found. |
| lastIndexOf | | protected static int lastIndexOf(Object elem, Object[] elementData, int len)(Code) | | |
| lastIndexOf | | public int lastIndexOf(Object elem, int index)(Code) | | Searches backwards for the specified object, starting from the specified
index, and returns an index to it.
Parameters:
elem - the desired component.
Parameters:
index - the index to start searching from. the index of the last occurrence of the specified object in thisList at position less than index in the List; -1 if the object isnot found. |
| listIterator | | public ListIterator listIterator()(Code) | | Returns an Iterator of the elements in this List (in proper sequence).
The iterator provides a snapshot of the state of the list when the
iterator was constructed. No synchronization is needed while traversing
the iterator. The iterator does NOT support the
remove, set, or add
methods.
|
| listIterator | | public ListIterator listIterator(int index)(Code) | | Returns a ListIterator of 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
nextElement. An initial call to previousElement would return the element
with the specified index minus one. The ListIterator returned by this
implementation will throw an UnsupportedOperationException in its remove,
set and add methods.
Parameters:
index - index of first element to be returned from the ListIterator(by a call to getNext).
exception:
IndexOutOfBoundsException - index is out of range (index < 0 || index > size()). |
| rangeCheck | | protected void rangeCheck(int index, int length)(Code) | | Check if the given index is in range. If not, throw an appropriate
runtime exception.
Parameters:
index -
Parameters:
length - |
| remove | | public synchronized Object remove(int index)(Code) | | Removes the element at the specified position in this list. Shifts any
subsequent elements to the left (subtracts one from their indices).
Returns the element that was removed from the list.
Parameters:
index - the index of the element to removed.
exception:
IndexOutOfBoundsException - index out of range (index < 0 || index >= size()). |
| remove | | public synchronized boolean remove(Object element)(Code) | | Removes a single instance of the specified element from this Collection,
if it is present (optional operation). More formally, removes an 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).
Parameters:
element - element to be removed from this Collection, if present. true if the Collection changed as a result of the call. |
| removeAll | | public synchronized boolean removeAll(Collection c)(Code) | | Removes from this Collection all of its elements that are contained in
the specified Collection. This is a particularly expensive operation in
this class because of the need for an internal temporary array.
true if this Collection changed as a result of the call. |
| removeRange | | public synchronized void removeRange(int fromIndex, int toIndex)(Code) | | 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 - index of first element to be removed.
Parameters:
toIndex - index after last element to be removed.
exception:
IndexOutOfBoundsException - fromIndex or toIndex out of range (fromIndex < 0 ||fromIndex >= size() || toIndex > size() || toIndex< fromIndex). |
| retainAll | | public synchronized boolean retainAll(Collection c)(Code) | | Retains only the elements in this Collection that are contained in the
specified Collection (optional operation). In other words, removes from
this Collection all of its elements that are not contained in the
specified Collection.
true if this Collection changed as a result of the call. |
| set | | public synchronized Object set(int index, Object element)(Code) | | Replaces the element at the specified position in this list with the
specified element.
Parameters:
index - index of element to replace.
Parameters:
element - element to be stored at the specified position. the element previously at the specified position.
exception:
IndexOutOfBoundsException - index out of range (index < 0 || index >= size()). |
| size | | public int size()(Code) | | Returns the number of components in this list.
the number of components in this list. |
| subList | | public synchronized List subList(int fromIndex, int toIndex)(Code) | | Returns a view of the portion of this List between fromIndex, inclusive,
and toIndex, exclusive. The returned List is backed by this List, so
changes in the returned List are reflected in this List, and vice-versa.
While mutative operations are supported, they are probably not very
useful for CopyOnWriteArrays.
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 the List, or otherwise perturb it in such a
fashion that iterations in progress may yield incorrect results.)
Parameters:
fromIndex - low endpoint (inclusive) of the subList.
Parameters:
toKey - high endpoint (exclusive) of the subList. a view of the specified range within this List.
exception:
IndexOutOfBoundsException - Illegal endpoint index value (fromIndex < 0 || toIndex> size || fromIndex > toIndex). |
| toArray | | public Object[] toArray()(Code) | | Returns an array containing all of the elements in this list in the
correct order.
|
| toArray | | public Object[] toArray(Object a)(Code) | | 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. 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 - the array into which the elements of the list are to bestored, if it is big enough; otherwise, a new array of thesame runtime type is allocated for this purpose. an array containing the elements of the list.
exception:
ArrayStoreException - the runtime type of a is not a supertype of the runtimetype of every element in this list. |
| toString | | public String toString()(Code) | | Returns a string representation of this Collection, containing the String
representation of each element.
|
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