ConcurrentLinkedDeque

public class ConcurrentLinkedDeque extends AbstractCollection<E>
implements Deque<E> Serializable

An unbounded concurrent {@linkplain Deque deque} based on linked nodes. Concurrent insertion, removal, and access operations execute safely across multiple threads. A 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.

Public Constructor Summary

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.

Public Method Summary

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 the specified element.
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 occurrence of the specified element from this deque.
E
removeFirst()
Retrieves and removes the first element of this deque.
boolean
removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element from this deque.
E
removeLast()
Retrieves and removes the last element of this deque.
boolean
removeLastOccurrence(Object o)
Removes the last occurrence of the specified element from 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.
String
toString()
Returns a string representation of this collection.

Protected Method Summary

void
finalize()
Invoked when the garbage collector has detected that this instance is no longer reachable.

Inherited Method Summary