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CopyOnWriteArrayList empty = new CopyOnWriteArrayList();
Based on 25 examples
public class CopyOnWriteArrayList extends Object implements List, RandomAccess, Cloneable, Serializable
A thread-safe variant of {@link 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 may be more efficient than alternatives when traversal operations vastly outnumber mutations, and is useful when you cannot or don't want to synchronize traversals, yet need to preclude interference among concurrent threads. The "snapshot" style 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 and the iterator is guaranteed not to throw ConcurrentModificationException. The iterator will not reflect additions, removals, or changes to the list since the iterator was created. Element-changing operations on iterators themselves (remove, set, and add) are not supported. These methods throw UnsupportedOperationException.
All elements are permitted, including null.
Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a {@code CopyOnWriteArrayList} happen-before actions subsequent to the access or removal of that element from the {@code CopyOnWriteArrayList} in another thread.
This class is a member of the Java Collections Framework.
Constructor Summary | |
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Creates an empty list. |
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Creates a list containing the elements of the specified collection, in the order they are returned by the collection's iterator. |
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CopyOnWriteArrayList(Object[] toCopyIn) Creates a list holding a copy of the given array. |
Method Summary | |
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boolean |
Appends the specified element to the end of this list. |
void |
Inserts the specified element at the specified position in 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 |
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 |
Append the element if not present. |
void |
clear() Removes all of the elements from this list. |
Object |
clone() Returns a shallow copy of this list. |
boolean |
Returns true if this list contains the specified element. |
boolean |
Returns true if this list contains all of the elements of the specified collection. |
boolean |
Compares the specified object with this list for equality. |
Object |
get(int index) |
int |
hashCode() Returns the hash code value for this list. |
int |
Returns the index of the first occurrence of the specified element in this list, searching forwards from index, or returns -1 if the element is not found. |
int |
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boolean |
isEmpty() Returns true if this list contains no elements. |
Iterator |
iterator() Returns an iterator over the elements in this list in proper sequence. |
int |
lastIndexOf(Object e, int index) Returns the index of the last occurrence of the specified element in this list, searching backwards from index, or returns -1 if the element is not found. |
int |
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ListIterator |
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ListIterator |
listIterator(int index) |
Object |
remove(int index) Removes the element at the specified position in this list. |
boolean |
Removes the first occurrence of the specified element from this list, if it is present. |
boolean |
Removes from this list all of its elements that are contained in the specified collection. |
boolean |
Retains only the elements in this list that are contained in the specified collection. |
Object |
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 |
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 proper sequence (from first to last element). |
Object[] |
Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. |
String |
toString() Returns a string representation of this list. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public CopyOnWriteArrayList()
public CopyOnWriteArrayList(Collection c)
c
- the collection of initially held elementspublic CopyOnWriteArrayList(Object[] toCopyIn)
toCopyIn
- the array (a copy of this array is used as the
internal array)Method Detail |
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public boolean add(Object e)
e
- element to be appended to this listpublic void add(int index, Object element)
index
element
public boolean addAll(Collection c)
c
- collection containing elements to be added to this listpublic boolean addAll(int index, Collection c)
index
- index at which to insert the first element
from the specified collectionc
- collection containing elements to be added to this listpublic int addAllAbsent(Collection c)
c
- collection containing elements to be added to this listpublic boolean addIfAbsent(Object e)
e
- element to be added to this list, if absentpublic void clear()
public Object clone()
clone
in class Object
public boolean contains(Object o)
o
- element whose presence in this list is to be testedpublic boolean containsAll(Collection c)
c
- collection to be checked for containment in this listpublic boolean equals(Object o)
equals
in class Object
o
- the object to be compared for equality with this listpublic Object get(int index)
index
public int hashCode()
This implementation uses the definition in {@link List#hashCode}.
hashCode
in class Object
public int indexOf(Object e, int index)
e
- element to search forindex
- index to start searching frompublic int indexOf(Object o)
o
public boolean isEmpty()
public Iterator iterator()
The returned 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.
public int lastIndexOf(Object e, int index)
e
- element to search forindex
- index to start searching backwards frompublic int lastIndexOf(Object o)
o
public ListIterator listIterator()
The returned 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.
public ListIterator listIterator(int index)
The returned 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.
index
public Object remove(int index)
index
public boolean remove(Object o)
o
- element to be removed from this list, if presentpublic boolean removeAll(Collection c)
c
- collection containing elements to be removed from this listpublic boolean retainAll(Collection c)
c
- collection containing elements to be retained in this listpublic Object set(int index, Object element)
index
element
public int size()
public List subList(int fromIndex, int toIndex)
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.)
fromIndex
- low endpoint (inclusive) of the subListtoIndex
- high endpoint (exclusive) of the subListpublic Object[] toArray()
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.
public Object[] toArray(Object[] a)
If this list fits in the specified array with room to spare (i.e., the array has more elements than this list), the element in the array immediately following the end of the list is set to null. (This is useful in determining the length of this list only if the caller knows that this list does not contain any null elements.)
Like the {@link #toArray()} method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.
Suppose x is a list known to contain only strings. The following code can be used to dump the list into a newly allocated array of String:
String[] y = x.toArray(new String[0]);Note that toArray(new Object[0]) is identical in function to toArray().
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.public String toString()
toString
in class Object
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