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FlexDoc/Javadoc 2.0 Demo Java Doc |
Class DelayQueue<E extends
Delayed>
java.util.concurrent.DelayQueue<E>
Type Parameters:
E - the type of elements held in this queue
All Implemented Interfaces:
public class
DelayQueue<E extends Delayed>
An unbounded
blocking queue of
Delayed elements, in which an element can only be taken
when its delay has expired. The
head of the queue is that
Delayed element whose delay expired furthest in the
past. If no delay has expired there is no head and
poll
will return
null. Expiration occurs when an element's
getDelay(TimeUnit.NANOSECONDS) method returns a value less
than or equal to zero. Even though unexpired elements cannot be
removed using
take or
poll, they are otherwise
treated as normal elements. For example, the
size method
returns the count of both expired and unexpired elements.
This queue does not permit null elements.
This class and its iterator implement all of the optional
methods of the Collection and Iterator interfaces.
The Iterator provided in method iterator() is not
guaranteed to traverse the elements of the DelayQueue in any
particular order.
This class is a member of the
Java Collections Framework.
Since:
1.5
Author:
Doug Lea
Constructor Summary |
Creates a new DelayQueue that is initially empty.
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Creates a DelayQueue initially containing the elements of the
given collection of Delayed instances.
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Method Summary |
boolean |
Inserts the specified element into this delay queue.
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void |
Atomically removes all of the elements from this delay queue.
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int |
Removes all available elements from this queue and adds them
to the given collection.
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int |
Removes at most the given number of available elements from
this queue and adds them to the given collection.
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Returns an iterator over all the elements (both expired and
unexpired) in this queue.
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boolean |
Inserts the specified element into this delay queue.
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boolean |
Inserts the specified element into this delay queue.
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Retrieves, but does not remove, the head of this queue, or
returns null if this queue is empty.
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Retrieves and removes the head of this queue, or returns null
if this queue has no elements with an expired delay.
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Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue,
or the specified wait time expires.
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void |
Inserts the specified element into this delay queue.
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int |
Always returns Integer.MAX_VALUE because
a DelayQueue is not capacity constrained.
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boolean |
Removes a single instance of the specified element from this
queue, if it is present, whether or not it has expired.
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int |
Returns the number of elements in this collection.
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Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue.
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Returns an array containing all of the elements in this queue.
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Returns an array containing all of the elements in this queue; the
runtime type of the returned array is that of the specified array.
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Methods inherited from class java.lang. Object |
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Methods inherited from interface java.util. Collection |
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Methods inherited from interface java.lang. Iterable |
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Creates a new DelayQueue that is initially empty.
Creates a
DelayQueue initially containing the elements of the
given collection of
Delayed instances.
Parameters:
c - the collection of elements to initially contain
Throws:
Inserts the specified element into this delay queue.
Specified by:
Overrides:
Parameters:
e - the element to add
Returns:
Throws:
Inserts the specified element into this delay queue.
Specified by:
Parameters:
e - the element to add
Returns:
true
Throws:
Inserts the specified element into this delay queue. As the queue is
unbounded this method will never block.
Specified by:
Parameters:
e - the element to add
Throws:
Inserts the specified element into this delay queue. As the queue is
unbounded this method will never block.
Specified by:
Parameters:
e - the element to add
timeout - This parameter is ignored as the method never blocks
unit - This parameter is ignored as the method never blocks
Returns:
true
Throws:
Retrieves and removes the head of this queue, or returns
null
if this queue has no elements with an expired delay.
Specified by:
Returns:
the head of this queue, or null if this
queue has no elements with an expired delay
Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue.
Specified by:
Returns:
the head of this queue
Throws:
Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue,
or the specified wait time expires.
Specified by:
Parameters:
timeout - how long to wait before giving up, in units of
unit
unit - a TimeUnit determining how to interpret the
timeout parameter
Returns:
the head of this queue, or null if the
specified waiting time elapses before an element with
an expired delay becomes available
Throws:
Retrieves, but does not remove, the head of this queue, or
returns
null if this queue is empty. Unlike
poll, if no expired elements are available in the queue,
this method returns the element that will expire next,
if one exists.
Specified by:
Returns:
the head of this queue, or null if this
queue is empty
Returns the number of elements in this collection. If this collection
contains more than Integer.MAX_VALUE elements, returns
Integer.MAX_VALUE.
Specified by:
Overrides:
Returns:
the number of elements in this collection
Removes all available elements from this queue and adds them
to the given collection. This operation may be more
efficient than repeatedly polling this queue. A failure
encountered while attempting to add elements to
collection c may result in elements being in neither,
either or both collections when the associated exception is
thrown. Attempts to drain a queue to itself result in
IllegalArgumentException. Further, the behavior of
this operation is undefined if the specified collection is
modified while the operation is in progress.
Specified by:
Parameters:
c - the collection to transfer elements into
Returns:
the number of elements transferred
Throws:
UnsupportedOperationException - if addition of elements
is not supported by the specified collection
ClassCastException - if the class of an element of this queue
prevents it from being added to the specified collection
IllegalArgumentException - if the specified collection is this
queue, or some property of an element of this queue prevents
it from being added to the specified collection
Removes at most the given number of available elements from
this queue and adds them to the given collection. A failure
encountered while attempting to add elements to
collection c may result in elements being in neither,
either or both collections when the associated exception is
thrown. Attempts to drain a queue to itself result in
IllegalArgumentException. Further, the behavior of
this operation is undefined if the specified collection is
modified while the operation is in progress.
Specified by:
Parameters:
c - the collection to transfer elements into
maxElements - the maximum number of elements to transfer
Returns:
the number of elements transferred
Throws:
UnsupportedOperationException - if addition of elements
is not supported by the specified collection
ClassCastException - if the class of an element of this queue
prevents it from being added to the specified collection
IllegalArgumentException - if the specified collection is this
queue, or some property of an element of this queue prevents
it from being added to the specified collection
Atomically removes all of the elements from this delay queue.
The queue will be empty after this call returns.
Elements with an unexpired delay are not waited for; they are
simply discarded from the queue.
Specified by:
Overrides:
public int remainingCapacity |
() |
Always returns
Integer.MAX_VALUE because
a
DelayQueue is not capacity constrained.
Specified by:
Returns:
Integer.MAX_VALUE
Returns an array containing all of the elements in this queue.
The returned array elements are in no particular order.
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.
Specified by:
Overrides:
Returns:
an array containing all of the elements in this queue
Returns an array containing all of the elements in this queue; the
runtime type of the returned array is that of the specified array.
The returned array elements are in no particular order.
If the queue fits in the specified array, it is returned therein.
Otherwise, a new array is allocated with the runtime type of the
specified array and the size of this queue.
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.
The following code can be used to dump a delay queue into a newly
allocated array of Delayed:
Delayed[] a = q.toArray(new Delayed[0]);
Note that
toArray(new Object[0]) is identical in function to
toArray().
Specified by:
Overrides:
Type Parameters:
T - the component type of the array to contain the collection
Parameters:
a - the array into which the elements of the queue are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purpose
Returns:
an array containing all of the elements in this queue
Throws:
ArrayStoreException - if the runtime type of the specified array
is not a supertype of the runtime type of every element in
this queue
Removes a single instance of the specified element from this
queue, if it is present, whether or not it has expired.
Specified by:
Overrides:
Parameters:
o - element to be removed from this collection, if present
Returns:
true if an element was removed as a result of this call
Returns an iterator over all the elements (both expired and
unexpired) in this queue. The iterator does not return the
elements in any particular order.
The returned iterator is
weakly consistent.
Specified by:
Overrides:
Returns:
an iterator over the elements in this queue
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