Class Overview
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.
This queue does not permit null elements.
This class implements all of the optional methods
of the Collection and Iterator interfaces.
Summary
| Public Constructors |
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DelayQueue()
Creates a new DelayQueue that is initially empty.
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DelayQueue(Collection<? extends E> c)
Creates a DelayQueue initially containing the elements of the
given collection of Delayed instances. |
| Public Methods |
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boolean
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add(E o)
Adds the specified element to this queue.
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void
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clear()
Atomically removes all of the elements from this delay queue.
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int
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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.
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int
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drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them
into the given collection.
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Iterator<E>
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iterator()
Returns an iterator over the elements in this queue.
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boolean
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offer(E o, long timeout, TimeUnit unit)
Inserts the specified element into this delay queue.
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boolean
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offer(E o)
Inserts the specified element into this delay queue.
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E
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peek()
Gets but not removes the element in the head of the queue, or throws
exception if there is no element in the queue.
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E
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poll(long time, TimeUnit unit)
Retrieves and removes the head of this queue, waiting
if necessary up to the specified wait time if no elements are
present on this queue.
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E
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poll()
Gets and removes the element in the head of the queue, or returns null if
there is no element in the queue.
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void
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put(E o)
Adds the specified element to this delay queue.
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int
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remainingCapacity()
Always returns Integer.MAX_VALUE because
a DelayQueue is not capacity constrained.
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boolean
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remove(Object o)
Removes the first occurrence of the specified object from this
Collection.
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int
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size()
Returns the number of elements in this Collection.
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E
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take()
Retrieves and removes the head of this queue, waiting
if no elements are present on this queue.
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<T>
T[]
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toArray(T[] array)
Returns an array containing all elements contained in this Collection.
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Object[]
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toArray()
Returns a new array containing all elements contained in this Collection.
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[Expand]
Inherited Methods |
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From class java.util.AbstractQueue
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boolean
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add(E o)
Adds an element to the queue.
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boolean
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addAll(Collection<? extends E> c)
Adds all the elements of a collection to the queue.
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void
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clear()
Removes all elements of the queue.
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E
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element()
Gets but not removes the element in the head of the queue.
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E
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remove()
Gets and removes the element in the head of the queue.
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From class java.util.AbstractCollection
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boolean
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add(E object)
If the specified element is not contained within this collection, and
addition of this element succeeds, then true will be returned.
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boolean
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addAll(Collection<? extends E> collection)
Adds the objects in the specified Collection to this Collection.
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void
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clear()
Removes all the elements in this collection.
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boolean
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contains(Object object)
Searches this Collection for the specified object.
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boolean
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containsAll(Collection<?> collection)
Searches this Collection for all objects in the specified Collection.
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boolean
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isEmpty()
Returns true if the collection has no element, otherwise false.
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abstract
Iterator<E>
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iterator()
Returns an Iterator on the elements of this Collection.
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boolean
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remove(Object object)
Removes the first occurrence of the specified object from this
Collection.
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boolean
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removeAll(Collection<?> collection)
Removes all occurrences in this Collection of each object in the
specified Collection.
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boolean
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retainAll(Collection<?> collection)
Removes all objects from this Collection that are not contained in the
specified Collection.
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abstract
int
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size()
Returns the number of elements in this Collection.
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<T>
T[]
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toArray(T[] contents)
Returns an array containing all elements contained in this Collection.
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Object[]
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toArray()
Returns a new array containing all elements contained in this Collection.
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String
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toString()
Returns the string representation of this Collection.
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From class java.lang.Object
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Object
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clone()
Returns a new instance of the same class as the receiver, whose slots
have been filled in with the values in the slots of the receiver.
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boolean
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equals(Object o)
Compares the argument to the receiver, and returns true if they represent
the same object using a class specific comparison.
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void
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finalize()
Called by the virtual machine when there are no longer any (non-weak)
references to the receiver.
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final
Class<? extends Object>
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getClass()
Returns the unique instance of java.lang.Class which represents the class
of the receiver.
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int
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hashCode()
Returns an integer hash code for the receiver.
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final
void
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notify()
Causes one thread which is wait ing on the receiver to be
made ready to run.
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final
void
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notifyAll()
Causes all threads which are wait ing on the receiver to
be made ready to run.
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String
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toString()
Returns a string containing a concise, human-readable description of the
receiver.
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final
void
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wait(long time, int frac)
Causes the thread which sent this message to be made not ready to run
either pending some change in the receiver (as indicated by
notify or notifyAll) or the expiration of
the timeout.
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final
void
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wait(long time)
Causes the thread which sent this message to be made not ready to run
either pending some change in the receiver (as indicated by
notify or notifyAll) or the expiration of
the timeout.
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final
void
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wait()
Causes the thread which sent this message to be made not ready to run
pending some change in the receiver (as indicated by notify
or notifyAll).
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From interface java.lang.Iterable
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From interface java.util.Collection
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abstract
boolean
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add(E object)
Attempts to add object to the contents of this
Collection.
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abstract
boolean
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addAll(Collection<? extends E> collection)
Attempts to add all of the objects contained in collection
to the contents of this collection.
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abstract
void
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clear()
Removes all elements from this Collection, leaving it empty.
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abstract
boolean
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contains(Object object)
Searches this Collection for the specified object.
|
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abstract
boolean
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containsAll(Collection<?> collection)
Searches this Collection for all objects in the specified Collection.
|
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abstract
boolean
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equals(Object object)
Compares the argument to the receiver, and returns true if they represent
the same object using a class specific comparison.
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abstract
int
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hashCode()
Returns an integer hash code for the receiver.
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abstract
boolean
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isEmpty()
Returns if this Collection has no elements, a size of zero.
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abstract
Iterator<E>
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iterator()
Returns an instance of Iterator that may be used to access the
objects contained by this collection. |
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abstract
boolean
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remove(Object object)
Removes the first occurrence of the specified object from this
Collection.
|
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abstract
boolean
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removeAll(Collection<?> collection)
Removes all occurrences in this Collection of each object in the
specified Collection.
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abstract
boolean
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retainAll(Collection<?> collection)
Removes all objects from this Collection that are not also found in the
contents of collection.
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abstract
int
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size()
Returns a count of how many objects are contained by this collection.
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abstract
<T>
T[]
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toArray(T[] array)
Returns an array containing all elements contained in this Collection.
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abstract
Object[]
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toArray()
Returns a new array containing all elements contained in this Collection.
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From interface java.util.Queue
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abstract
E
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element()
Gets but not removes the element in the head of the queue.
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abstract
boolean
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offer(E o)
Inserts the specified element into the queue provided that the condition
allows such an operation.
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abstract
E
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peek()
Gets but not removes the element in the head of the queue, or throws
exception if there is no element in the queue.
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abstract
E
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poll()
Gets and removes the element in the head of the queue, or returns null if
there is no element in the queue.
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abstract
E
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remove()
Gets and removes the element in the head of the queue.
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From interface java.util.concurrent.BlockingQueue
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abstract
boolean
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add(E o)
Adds the specified element to this queue if it is possible to
do so immediately, returning true upon success, else
throwing an IllegalStateException.
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abstract
int
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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.
|
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abstract
int
|
drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them
into the given collection.
|
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abstract
boolean
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offer(E o)
Inserts the specified element into this queue, if possible.
|
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abstract
boolean
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offer(E o, long timeout, TimeUnit unit)
Inserts the specified element into this queue, waiting if necessary
up to the specified wait time for space to become available.
|
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abstract
E
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poll(long timeout, TimeUnit unit)
Retrieves and removes the head of this queue, waiting
if necessary up to the specified wait time if no elements are
present on this queue.
|
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abstract
void
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put(E o)
Adds the specified element to this queue, waiting if necessary for
space to become available.
|
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abstract
int
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remainingCapacity()
Returns the number of elements that this queue can ideally (in
the absence of memory or resource constraints) accept without
blocking, or Integer.MAX_VALUE if there is no
intrinsic limit.
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abstract
E
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take()
Retrieves and removes the head of this queue, waiting
if no elements are present on this queue.
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Public Constructors
public
DelayQueue
()
Creates a new DelayQueue that is initially empty.
public
DelayQueue
(Collection<? extends E> c)
Creates a DelayQueue initially containing the elements of the
given collection of Delayed instances.
Public Methods
public
boolean
add
(E o)
Adds the specified element to this queue.
Returns
- true (as per the general contract of
Collection.add).
public
void
clear
()
Atomically removes all of the elements from this delay queue.
The queue will be empty after this call returns.
public
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. 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.
Parameters
| c
| the collection to transfer elements into |
| maxElements
| the maximum number of elements to transfer |
Returns
- the number of elements transferred.
public
int
drainTo
(Collection<? super E> c)
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.
Parameters
| c
| the collection to transfer elements into |
Returns
- the number of elements transferred.
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.
Returns
- an iterator over the elements in this queue.
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.
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 |
public
boolean
offer
(E o)
Inserts the specified element into this delay queue.
public
E
peek
()
Gets but not removes the element in the head of the queue, or throws
exception if there is no element in the queue.
Returns
- the element in the head of the queue or null if there is no
element in the queue.
public
E
poll
(long time, TimeUnit unit)
Retrieves and removes the head of this queue, waiting
if necessary up to the specified wait time if no elements are
present on this queue.
Parameters
| 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 is present.
public
E
poll
()
Gets and removes the element in the head of the queue, or returns null if
there is no element in the queue.
Returns
- the element in the head of the queue or null if there is no
element in the queue.
public
void
put
(E o)
Adds the specified element to this delay queue. As the queue is
unbounded this method will never block.
public
int
remainingCapacity
()
Always returns Integer.MAX_VALUE because
a DelayQueue is not capacity constrained.
public
boolean
remove
(Object o)
Removes the first occurrence of the specified object from this
Collection. This operation traverses over the collection, looking
for the specified object. Once the object is found, the object will
be removed from the collection using the iterator's remove method.
This collection will throw an UnsupportedOperationException if the
iterator returned does not implement remove method, and the specified
object is in this collection.
Returns
- true if this Collection is modified, false otherwise
public
int
size
()
Returns the number of elements in this Collection.
Returns
- the number of elements in this Collection
public
E
take
()
Retrieves and removes the head of this queue, waiting
if no elements are present on this queue.
public
T[]
toArray
(T[] array)
Returns an array containing all elements contained in this Collection. If
the specified array is large enough to hold the elements, the specified
array is used, otherwise an array of the same type is created. If the
specified array is used and is larger than this Collection, the array
element following the collection elements is set to null.
Returns
- an array of the elements from this Collection
public
Object[]
toArray
()
Returns a new array containing all elements contained in this Collection.
All the elements in the array will not be referenced by the collection.
The elements in the returned array will be sorted to the same order as
those returned by the iterator of this collection itself if the collection
guarantees the order.
Returns
- an array of the elements from this Collection
