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java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
java.util.concurrent.ConcurrentLinkedQueue<E>
Collection
and Iterator
interfaces.
Memory consistency effects: As with other concurrent
collections, actions in a thread prior to placing an object into a
ConcurrentLinkedQueue
happen-before
actions subsequent to the access or removal of that element from
the ConcurrentLinkedQueue
in another thread.
This class is a member of the
../../../../technotes/guides/collections/index.html">
Java Collections Framework.
Constructor Summary | |
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Method Summary | |
boolean |
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boolean | |
boolean |
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Iterator |
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boolean |
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E |
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E |
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boolean | |
int |
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Methods inherited from class java.util.AbstractCollection<E> | |
T[] toArray , add , addAll , clear , contains , containsAll , isEmpty , iterator , remove , removeAll , retainAll , size , toArray , toString |
Methods inherited from class java.lang.Object | |
clone , equals , extends Object> getClass , finalize , hashCode , notify , notifyAll , toString , wait , wait , wait |
public ConcurrentLinkedQueue()
Creates a ConcurrentLinkedQueue that is initially empty.
public ConcurrentLinkedQueue(E> c)
Creates a ConcurrentLinkedQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator.
- Parameters:
c
- the collection of elements to initially contain
- Throws:
NullPointerException
- if the specified collection or any of its elements are null
public boolean add(E e)
Inserts the specified element at the tail of this queue.
- Specified by:
- add in interface Queue<E>
- add in interface Collection<E>
- Overrides:
- add in interface AbstractQueue<E>
- Returns:
- true (as specified by
Collection.add(E)
)
- Throws:
NullPointerException
- if the specified element is null
public boolean contains(Object o)
Returns true if this queue contains the specified element. More formally, returns true if and only if this queue contains at least one element e such that o.equals(e).
- Specified by:
- contains in interface Collection<E>
- Overrides:
- contains in interface AbstractCollection<E>
- Parameters:
o
- object to be checked for containment in this queue
- Returns:
- true if this queue contains the specified element
public boolean isEmpty()
Returns true if this queue contains no elements.
- Specified by:
- isEmpty in interface Collection<E>
- Overrides:
- isEmpty in interface AbstractCollection<E>
- Returns:
- true if this queue contains no elements
public Iteratoriterator()
Returns an iterator over the elements in this queue in proper sequence. The returned iterator is a "weakly consistent" iterator that will never throwConcurrentModificationException
, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.
- Specified by:
- iterator in interface Collection<E>
- iterator in interface Iterable<E>
- Overrides:
- iterator in interface AbstractCollection<E>
- Returns:
- an iterator over the elements in this queue in proper sequence
public boolean offer(E e)
Inserts the specified element at the tail of this queue.
- Returns:
- true (as specified by
Queue.offer(E)
)
- Throws:
NullPointerException
- if the specified element is null
public E peek()
Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
- Returns:
- the head of this queue, or null if this queue is empty
public E poll()
Retrieves and removes the head of this queue, or returns null if this queue is empty.
- Returns:
- the head of this queue, or null if this queue is empty
public boolean remove(Object o)
Removes a single instance of the specified element from this queue, if it is present. More formally, removes an element e such that o.equals(e), if this queue contains one or more such elements. Returns true if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).
- Specified by:
- remove in interface Collection<E>
- Overrides:
- remove in interface AbstractCollection<E>
- Parameters:
o
- element to be removed from this queue, if present
- Returns:
- true if this queue changed as a result of the call
public int size()
Returns the number of elements in this queue. If this queue contains more than Integer.MAX_VALUE elements, 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 queues, determining the current number of elements requires an O(n) traversal.
- Specified by:
- size in interface Collection<E>
- Overrides:
- size in interface AbstractCollection<E>
- Returns:
- the number of elements in this queue
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