E - the type of elements held in this collectionpublic class ConcurrentLinkedDeque<E> extends AbstractCollection<E> implements Deque<E>, Serializable
ConcurrentLinkedDeque is an appropriate choice when
many threads will share access to a common collection.
Like most other concurrent collection implementations, this class
does not permit the use of null elements.
Iterators and spliterators are weakly consistent.
Beware that, unlike in most collections, the size method
is NOT a constant-time operation. Because of the
asynchronous nature of these deques, determining the current number
of elements requires a traversal of the elements, and so may report
inaccurate results if this collection is modified during traversal.
Additionally, the bulk operations addAll,
removeAll, retainAll, containsAll,
equals, and toArray are not guaranteed
to be performed atomically. For example, an iterator operating
concurrently with an addAll operation might view only some
of the added elements.
This class and its iterator implement all of the optional
methods of the Deque and Iterator interfaces.
Memory consistency effects: As with other concurrent collections,
actions in a thread prior to placing an object into a
ConcurrentLinkedDeque
happen-before
actions subsequent to the access or removal of that element from
the ConcurrentLinkedDeque in another thread.
This class is a member of the Java Collections Framework.
| Constructor and Description |
|---|
ConcurrentLinkedDeque()
Constructs an empty deque.
|
ConcurrentLinkedDeque(Collection<? extends E> c)
Constructs a deque initially containing the elements of
the given collection, added in traversal order of the
collection's iterator.
|
| Modifier and Type | Method and Description |
|---|---|
boolean |
add(E e)
Inserts the specified element at the tail of this deque.
|
boolean |
addAll(Collection<? extends E> c)
Appends all of the elements in the specified collection to the end of
this deque, in the order that they are returned by the specified
collection's iterator.
|
void |
addFirst(E e)
Inserts the specified element at the front of this deque.
|
void |
addLast(E e)
Inserts the specified element at the end of this deque.
|
void |
clear()
Removes all of the elements from this deque.
|
boolean |
contains(Object o)
Returns
true if this deque contains at least one
element e such that o.equals(e). |
Iterator<E> |
descendingIterator()
Returns an iterator over the elements in this deque in reverse
sequential order.
|
E |
element()
Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first element of this deque).
|
E |
getFirst()
Retrieves, but does not remove, the first element of this deque.
|
E |
getLast()
Retrieves, but does not remove, the last element of this deque.
|
boolean |
isEmpty()
Returns
true if this collection contains no elements. |
Iterator<E> |
iterator()
Returns an iterator over the elements in this deque in proper sequence.
|
boolean |
offer(E e)
Inserts the specified element at the tail of this deque.
|
boolean |
offerFirst(E e)
Inserts the specified element at the front of this deque.
|
boolean |
offerLast(E e)
Inserts the specified element at the end of this deque.
|
E |
peek()
Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first element of this deque), or
returns
null if this deque is empty. |
E |
peekFirst()
Retrieves, but does not remove, the first element of this deque,
or returns
null if this deque is empty. |
E |
peekLast()
Retrieves, but does not remove, the last element of this deque,
or returns
null if this deque is empty. |
E |
poll()
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque), or returns
null if this deque is empty. |
E |
pollFirst()
Retrieves and removes the first element of this deque,
or returns
null if this deque is empty. |
E |
pollLast()
Retrieves and removes the last element of this deque,
or returns
null if this deque is empty. |
E |
pop()
Pops an element from the stack represented by this deque.
|
void |
push(E e)
Pushes an element onto the stack represented by this deque (in other
words, at the head of this deque) if it is possible to do so
immediately without violating capacity restrictions, throwing an
IllegalStateException if no space is currently available. |
E |
remove()
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
|
boolean |
remove(Object o)
Removes the first element
e such that
o.equals(e), if such an element exists in this deque. |
E |
removeFirst()
Retrieves and removes the first element of this deque.
|
boolean |
removeFirstOccurrence(Object o)
Removes the first element
e such that
o.equals(e), if such an element exists in this deque. |
E |
removeLast()
Retrieves and removes the last element of this deque.
|
boolean |
removeLastOccurrence(Object o)
Removes the last element
e such that
o.equals(e), if such an element exists in this deque. |
int |
size()
Returns the number of elements in this deque.
|
Spliterator<E> |
spliterator()
Returns a
Spliterator over the elements in this deque. |
Object[] |
toArray()
Returns an array containing all of the elements in this deque, in
proper sequence (from first to last element).
|
<T> T[] |
toArray(T[] a)
Returns an array containing all of the elements in this deque,
in proper sequence (from first to last element); the runtime
type of the returned array is that of the specified array.
|
containsAll, removeAll, retainAll, toStringclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitcontainsAll, equals, hashCode, parallelStream, removeAll, removeIf, retainAll, streampublic ConcurrentLinkedDeque()
public ConcurrentLinkedDeque(Collection<? extends E> c)
c - the collection of elements to initially containNullPointerException - if the specified collection or any
of its elements are nullpublic void addFirst(E e)
IllegalStateException.addFirst in interface Deque<E>e - the element to addNullPointerException - if the specified element is nullpublic void addLast(E e)
IllegalStateException.
This method is equivalent to add(E).
addLast in interface Deque<E>e - the element to addNullPointerException - if the specified element is nullpublic boolean offerFirst(E e)
false.offerFirst in interface Deque<E>e - the element to addtrue (as specified by Deque.offerFirst(E))NullPointerException - if the specified element is nullpublic boolean offerLast(E e)
false.
This method is equivalent to add(E).
offerLast in interface Deque<E>e - the element to addtrue (as specified by Deque.offerLast(E))NullPointerException - if the specified element is nullpublic E peekFirst()
Dequenull if this deque is empty.public E peekLast()
Dequenull if this deque is empty.public E getFirst()
DequepeekFirst only in that it
throws an exception if this deque is empty.getFirst in interface Deque<E>NoSuchElementException - if this deque is emptypublic E getLast()
DequepeekLast only in that it
throws an exception if this deque is empty.getLast in interface Deque<E>NoSuchElementException - if this deque is emptypublic E pollFirst()
Dequenull if this deque is empty.public E pollLast()
Dequenull if this deque is empty.public E removeFirst()
DequepollFirst only in that it throws an
exception if this deque is empty.removeFirst in interface Deque<E>NoSuchElementException - if this deque is emptypublic E removeLast()
DequepollLast only in that it throws an
exception if this deque is empty.removeLast in interface Deque<E>NoSuchElementException - if this deque is emptypublic boolean offer(E e)
false.offer in interface Deque<E>offer in interface Queue<E>e - the element to addtrue (as specified by Queue.offer(E))NullPointerException - if the specified element is nullpublic boolean add(E e)
IllegalStateException or return false.add in interface Collection<E>add in interface Deque<E>add in interface Queue<E>add in class AbstractCollection<E>e - element whose presence in this collection is to be ensuredtrue (as specified by Collection.add(E))NullPointerException - if the specified element is nullpublic E poll()
Dequenull if this deque is empty.
This method is equivalent to Deque.pollFirst().
public E peek()
Dequenull if this deque is empty.
This method is equivalent to Deque.peekFirst().
public E remove()
Dequepoll only in that it throws an
exception if this deque is empty.
This method is equivalent to Deque.removeFirst().
public E pop()
DequeThis method is equivalent to Deque.removeFirst().
pop in interface Deque<E>NoSuchElementException - if this deque is emptypublic E element()
Dequepeek only in that it throws an
exception if this deque is empty.
This method is equivalent to Deque.getFirst().
public void push(E e)
DequeIllegalStateException if no space is currently available.
This method is equivalent to Deque.addFirst(E).
push in interface Deque<E>e - the element to pushNullPointerException - if the specified element is null and this
deque does not permit null elementspublic boolean removeFirstOccurrence(Object o)
e such that
o.equals(e), if such an element exists in this deque.
If the deque does not contain the element, it is unchanged.removeFirstOccurrence in interface Deque<E>o - element to be removed from this deque, if presenttrue if the deque contained the specified elementNullPointerException - if the specified element is nullpublic boolean removeLastOccurrence(Object o)
e such that
o.equals(e), if such an element exists in this deque.
If the deque does not contain the element, it is unchanged.removeLastOccurrence in interface Deque<E>o - element to be removed from this deque, if presenttrue if the deque contained the specified elementNullPointerException - if the specified element is nullpublic boolean contains(Object o)
true if this deque contains at least one
element e such that o.equals(e).contains in interface Collection<E>contains in interface Deque<E>contains in class AbstractCollection<E>o - element whose presence in this deque is to be testedtrue if this deque contains the specified elementpublic boolean isEmpty()
true if this collection contains no elements.isEmpty in interface Collection<E>isEmpty in class AbstractCollection<E>true if this collection contains no elementspublic int size()
Integer.MAX_VALUE elements, it
returns Integer.MAX_VALUE.
Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these deques, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.
size in interface Collection<E>size in interface Deque<E>size in class AbstractCollection<E>public boolean remove(Object o)
e such that
o.equals(e), if such an element exists in this deque.
If the deque does not contain the element, it is unchanged.remove in interface Collection<E>remove in interface Deque<E>remove in class AbstractCollection<E>o - element to be removed from this deque, if presenttrue if the deque contained the specified elementNullPointerException - if the specified element is nullpublic boolean addAll(Collection<? extends E> c)
addAll of a deque to
itself result in IllegalArgumentException.addAll in interface Collection<E>addAll in class AbstractCollection<E>c - the elements to be inserted into this dequetrue if this deque changed as a result of the callNullPointerException - if the specified collection or any
of its elements are nullIllegalArgumentException - if the collection is this dequeAbstractCollection.add(Object)public void clear()
clear in interface Collection<E>clear in class AbstractCollection<E>public Object[] toArray()
The returned array will be "safe" in that no references to it are maintained by this deque. (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.
toArray in interface Collection<E>toArray in class AbstractCollection<E>public <T> T[] toArray(T[] a)
If this deque fits in the specified array with room to spare
(i.e., the array has more elements than this deque), the element in
the array immediately following the end of the deque is set to
null.
Like the 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 deque known to contain only strings.
The following code can be used to dump the deque 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().toArray in interface Collection<E>toArray in class AbstractCollection<E>T - the runtime type of the array to contain the collectiona - the array into which the elements of the deque are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purposeArrayStoreException - if the runtime type of the specified array
is not a supertype of the runtime type of every element in
this dequeNullPointerException - if the specified array is nullpublic Iterator<E> iterator()
The returned iterator is weakly consistent.
public Iterator<E> descendingIterator()
The returned iterator is weakly consistent.
descendingIterator in interface Deque<E>public Spliterator<E> spliterator()
Spliterator over the elements in this deque.
The returned spliterator is weakly consistent.
The Spliterator reports Spliterator.CONCURRENT,
Spliterator.ORDERED, and Spliterator.NONNULL.
spliterator in interface Iterable<E>spliterator in interface Collection<E>Spliterator implements trySplit to permit limited
parallelism.Spliterator over the elements in this deque Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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