This implementation employs an efficient "wait-free" algorithm based on one described in Simple, Fast, and Practical Non-Blocking and Blocking Concurrent Queue Algorithms by Maged M. Michael and Michael L. Scott.
Beware that, unlike in most collections, the size method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires a traversal of the elements.
This class and its iterator implement all of the optional methods of the 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 Java Collections Framework.
| Constructor Summary |
|---|
|
Creates a ConcurrentLinkedQueue that is initially empty. |
|
Creates a ConcurrentLinkedQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator. |
| Method Summary | |
|---|---|
| boolean |
Inserts the specified element at the tail of this queue. |
| boolean |
Returns true if this queue contains the specified element. |
| boolean |
Returns true if this queue contains no elements. |
| Iterator<E> |
Returns an iterator over the elements in this queue in proper sequence. |
| boolean |
Inserts the specified element at the tail of this queue. |
| E |
No description provided. |
| E |
No description provided. |
| boolean |
Removes a single instance of the specified element from this queue, if it is present. |
| int |
Returns the number of elements in this queue. |
| Object[] |
Returns an array containing all of the elements in this queue, in proper sequence. |
| T[] |
Returns an array containing all of the elements in this queue, in proper sequence; the runtime type of the returned array is that of the specified array. |
| Methods inherited from java.utilAbstractCollection |
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| Methods inherited from java.utilAbstractQueue |
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| Methods inherited from java.utilCollection |
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| Methods inherited from java.langObject |
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| Methods inherited from java.utilQueue |
|---|
public ConcurrentLinkedQueue
(
)
public
boolean
add
(
E
e
)
public
boolean
isEmpty
(
)
public
boolean
offer
(
E
e
)
public
E
peek
(
)
public
E
poll
(
)
public
int
size
(
)
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.
The returned array will be "safe" in that no references to it are maintained by this queue. (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 <T>
T[]
toArray
(
T
[]
a
)
If this queue fits in the specified array with room to spare (i.e., the array has more elements than this queue), the element in the array immediately following the end of the queue 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 queue known to contain only strings. The following code can be used to dump the queue 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(). 