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java.util.concurrent
Class DelayQueue<E extends
Delayed
>
java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
java.util.concurrent.DelayQueue<E>
-
-
Type Parameters:
-
E - the type of elements held in this collection
-
All Implemented Interfaces:
-
Iterable
<E>,
Collection
<E>,
BlockingQueue
<E>,
Queue
<E>
-
public class DelayQueue<E extends Delayed>
- extends AbstractQueue<E>
- implements BlockingQueue<E>
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
past - if
no delay has expired there is no head and
poll
will return
null
.
Expiration occurs when an element's
This queue does not permit
getDelay(TimeUnit.NANOSECONDS)
method returns a value less than or equal to zero. This queue does not permit
null
elements.
This class
and its iterator implement
implements
all of the optional methods of the
Collection
and
Iterator
interfaces.
This class is a member of the
Java Collections Framework
.
-
Since:
-
1.5
Constructor Summary
|
DelayQueue
()
Creates a new
DelayQueue
that is initially empty. |
DelayQueue
(
Collection
<? extends
E
> c)
Creates a
DelayQueue
initially containing the elements of the given collection of
Delayed
instances. |
Method Summary
|
boolean |
add
(
E
o)
Adds the specified element to this queue. |
void |
clear
()
Atomically removes all of the elements from this delay queue. |
int |
drainTo
(
Collection
<? super
E
> c)
Removes all available elements from this queue and adds them into the given collection. |
int |
drainTo
(
Collection
<? super
E
> c, int maxElements)
Removes at most the given number of available elements from this queue and adds them into the given collection. |
Iterator
<
E
> |
iterator
()
Returns an iterator over the elements in this queue. |
boolean |
offer
(
E
o)
Inserts the specified element into this delay queue. |
boolean |
offer
(
E
o, long timeout,
TimeUnit
unit)
Inserts the specified element into this delay queue. |
E
|
peek
()
Retrieves, but does not remove, the head of this queue, returning
null
if this queue
has no elements with an unexpired delay.
is empty.
|
E
|
poll
()
Retrieves and removes the head of this queue, or
null
if this queue
has no elements with an unexpired delay.
is empty.
|
E
|
poll
(long timeout,
(long time,
TimeUnit
Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time if no elements
with an unexpired delay
are present on this queue. |
void |
put
(
E
o)
Adds the specified element to this delay queue. |
int |
remainingCapacity
()
Always returns
Integer.MAX_VALUE
because a
DelayQueue
is not capacity constrained. |
boolean |
remove
(
Object
Removes a single instance of the specified element from this
queue,
collection,
if it is
present.
present (optional operation).
|
int |
size
()
Returns the number of elements in this collection. |
E
|
take
()
Retrieves and removes the head of this queue, waiting if no elements
with an unexpired delay
are present on this queue. |
Object
[] |
toArray
()
Returns an array containing all of the elements in this collection. |
|
toArray
(T[] array)
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. |
Methods inherited from class java.util.
AbstractQueue
|
addAll
,
element
,
remove
|
Methods inherited from class java.util.
AbstractCollection
|
contains
,
containsAll
,
isEmpty
,
removeAll
,
retainAll
,
toString
|
Methods inherited from class java.lang.
Object
|
clone
,
equals
,
finalize
,
getClass
,
hashCode
,
notify
,
notifyAll
,
wait
,
wait
,
wait
|
Methods inherited from interface java.util.
Queue
|
element
,
remove
|
DelayQueue
public DelayQueue()
-
Creates a new
DelayQueue
that is initially empty.
DelayQueue
public DelayQueue(Collection<? extends E> c)
-
Creates a
DelayQueue
initially containing the elements of the given collection of
Delayed
instances.
-
Parameters:
-
c - the collection
-
Throws:
-
NullPointerException
- if
c
or any element within it is
null
offer
public boolean offer(E o)
-
Inserts the specified element into this delay queue.
-
-
Specified by:
-
offer
in interface
BlockingQueue
<
E
extends
Delayed
>
-
Specified by:
-
offer
in interface
Queue
<
E
extends
Delayed
>
-
-
Parameters:
-
o - the element to add
-
Returns:
-
true
-
Throws:
-
NullPointerException
- if the specified element is
null
.
put
public void put(E o)
-
Adds the specified element to this delay queue. As the queue is unbounded this method will never block.
-
-
Specified by:
-
put
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Parameters:
-
o - the element to add
-
Throws:
-
NullPointerException
- if the specified element is
null
.
offer
public boolean offer(E o,
long timeout,
TimeUnit unit)
-
Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.
-
-
Specified by:
-
offer
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Parameters:
-
o - 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:
-
NullPointerException
- if the specified element is
null
.
add
public boolean add(E o)
-
Adds the specified element to this queue.
-
-
Specified by:
-
add
in interface
Collection
<
E
extends
Delayed
>
-
Specified by:
-
add
in interface
BlockingQueue
<
E
extends
Delayed
>
-
Overrides:
-
add
in class
AbstractQueue
<
E
extends
Delayed
>
-
-
Parameters:
-
o - the element to add
-
Returns:
-
true
(as per the general contract of
Collection.add
).
-
Throws:
-
NullPointerException
- if the specified element is
null
.
take
public E take()
throws InterruptedException
-
Description copied from interface:
BlockingQueue
-
Retrieves and removes the head of this queue, waiting if no elements
with an unexpired delay
are present on this queue.
-
-
Specified by:
-
take
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Returns:
-
the head of this queue
-
Throws:
-
InterruptedException
- if interrupted while waiting.
poll
public Epoll(long timeout,
(long time,
TimeUnit unit)
throws InterruptedException
-
Description copied from interface:
BlockingQueue
-
Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time if no elements
with an unexpired delay
are present on this queue.
-
-
Specified by:
-
poll
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Parameters:
-
timeout
time
- 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 unexpired delay
is present.
-
Throws:
-
InterruptedException
- if interrupted while waiting.
poll
public E poll()
-
Description copied from interface:
Queue
-
Retrieves and removes the head of this queue, or
null
if this queue has no elements with an unexpired delay.
if this queue is empty.
-
-
Specified by:
-
poll
in interface
Queue
<
E
extends
Delayed
>
-
-
Returns:
-
the head of this queue, or
null
if this queue has no elements with an unexpired delay.
if this queue is empty.
peek
public E peek()
-
Description copied from interface:
Queue
-
Retrieves, but does not remove, the head of this queue, returning
null
if this queue has no elements with an unexpired delay.
if this queue is empty.
-
-
Specified by:
-
peek
in interface
Queue
<
E
extends
Delayed
>
-
-
Returns:
-
the head of this queue, or
null
if this queue has no elements with an unexpired delay.
if this queue is empty.
size
public int size()
-
Description copied from class:
AbstractCollection
-
Returns the number of elements in this collection. If the collection contains more than
Integer.MAX_VALUE
elements, returns
Integer.MAX_VALUE
.
-
-
Specified by:
-
size
in interface
Collection
<
E
extends
Delayed
>
-
Specified by:
-
size
in class
AbstractCollection
<
E
extends
Delayed
>
-
-
Returns:
-
the number of elements in this collection.
drainTo
public int drainTo(Collection<? super E> c)
-
Description copied from interface:
BlockingQueue
-
Removes all available elements from this queue and adds them into 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:
-
drainTo
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Parameters:
-
c - the collection to transfer elements into
-
Returns:
-
the number of elements transferred.
drainTo
public int drainTo(Collection<? super E> c,
int maxElements)
-
Description copied from interface:
BlockingQueue
-
Removes at most the given number of available elements from this queue and adds them into 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:
-
drainTo
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Parameters:
-
c - the collection to transfer elements into
-
maxElements - the maximum number of elements to transfer
-
Returns:
-
the number of elements transferred.
clear
public void clear()
-
Atomically removes all of the elements from this delay queue. The queue will be empty after this call returns.
-
-
Specified by:
-
clear
in interface
Collection
<
E
extends
Delayed
>
-
Overrides:
-
clear
in class
AbstractQueue
<
E
extends
Delayed
>
-
remainingCapacity
public int remainingCapacity()
-
Always returns
Integer.MAX_VALUE
because a
DelayQueue
is not capacity constrained.
-
-
Specified by:
-
remainingCapacity
in interface
BlockingQueue
<
E
extends
Delayed
>
-
-
Returns:
-
Integer.MAX_VALUE
toArray
public Object[] toArray()
-
Description copied from class:
AbstractCollection
-
Returns an array containing all of the elements in this collection. If the collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array will be "safe" in that no references to it are maintained by the collection. (In other words, this method must allocate a new array even if the collection is backed by an Array). The caller is thus free to modify the returned array.
This implementation allocates the array to be returned, and iterates over the elements in the collection, storing each object reference in the next consecutive element of the array, starting with element 0.
-
-
Specified by:
-
toArray
in interface
Collection
<
E
extends
Delayed
>
-
Overrides:
-
toArray
in class
AbstractCollection
<
E
extends
Delayed
>
-
-
Returns:
-
an array containing all of the elements in this collection.
toArray
public <T> T[] toArray(T[] array)
-
Description copied from class:
AbstractCollection
-
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection 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 collection.
If the collection fits in the specified array with room to spare (i.e., the array has more elements than the collection), the element in the array immediately following the end of the collection is set to
null
. This is useful in determining the length of the collection
only
if the caller knows that the collection does not contain any
null
elements.)
If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
This implementation checks if the array is large enough to contain the collection; if not, it allocates a new array of the correct size and type (using reflection). Then, it iterates over the collection, storing each object reference in the next consecutive element of the array, starting with element 0. If the array is larger than the collection, a
null
is stored in the first location after the end of the collection.
-
-
Specified by:
-
toArray
in interface
Collection
<
E
extends
Delayed
>
-
Overrides:
-
toArray
in class
AbstractCollection
<
E
extends
Delayed
>
-
-
Parameters:
-
array - the array into which the elements of the collection 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 the elements of the collection.
remove
public boolean remove(Object o)
-
Removes a single instance of the specified element from this queue, if it is present.
Description copied from class:
AbstractCollection
-
Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element
e
such that
(o==null ? e==null : o.equals(e))
, if the collection contains one or more such elements. Returns
true
if the collection contained the specified element (or equivalently, if the collection changed as a result of the call).
This implementation iterates over the collection looking for the specified element. If it finds the element, it removes the element from the collection using the iterator's remove method.
Note that this implementation throws an
UnsupportedOperationException
if the iterator returned by this collection's iterator method does not implement the
remove
method and this collection contains the specified object.
-
-
Specified by:
-
remove
in interface
Collection
<
E
extends
Delayed
>
-
Overrides:
-
remove
in class
AbstractCollection
<
E
extends
Delayed
>
-
-
Parameters:
-
o - element to be removed from this collection, if present.
-
Returns:
-
true
if the collection contained the specified element.
iterator
public Iterator<E> iterator()
-
Returns an iterator over the elements in this queue. The iterator does not return the elements in any particular order. The returned iterator is a thread-safe "fast-fail" iterator that will throw
ConcurrentModificationException
upon detected interference.
-
-
Specified by:
-
iterator
in interface
Iterable
<
E
extends
Delayed
>
-
Specified by:
-
iterator
in interface
Collection
<
E
extends
Delayed
>
-
Specified by:
-
iterator
in class
AbstractCollection
<
E
extends
Delayed
>
-
-
Returns:
-
an iterator over the elements in this queue.