Class AbstractQueue<E>
- Type Parameters:
E
- the type of elements held in this queue
- All Implemented Interfaces:
Iterable<E>
,Collection<E>
,Queue<E>
- Direct Known Subclasses:
ArrayBlockingQueue
,ConcurrentLinkedQueue
,DelayQueue
,LinkedBlockingDeque
,LinkedBlockingQueue
,LinkedTransferQueue
,PriorityBlockingQueue
,PriorityQueue
,SynchronousQueue
Queue
operations. The implementations in this class are appropriate when
the base implementation does not allow null
elements. Methods add
, remove
, and
element
are based on offer
, poll
, and peek
, respectively, but throw
exceptions instead of indicating failure via false
or
null
returns.
A Queue
implementation that extends this class must
minimally define a method Queue.offer(E)
which does not permit
insertion of null
elements, along with methods Queue.peek()
, Queue.poll()
, Collection.size()
, and
Collection.iterator()
. Typically, additional methods will be
overridden as well. If these requirements cannot be met, consider
instead subclassing AbstractCollection
.
This class is a member of the Java Collections Framework.
- Since:
- 1.5
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionboolean
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returningtrue
upon success and throwing anIllegalStateException
if no space is currently available.boolean
addAll
(Collection<? extends E> c) Adds all of the elements in the specified collection to this queue.void
clear()
Removes all of the elements from this queue.element()
Retrieves, but does not remove, the head of this queue.remove()
Retrieves and removes the head of this queue.Methods inherited from class java.util.AbstractCollection
contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.Collection
contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray
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Constructor Details
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AbstractQueue
protected AbstractQueue()Constructor for use by subclasses.
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Method Details
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add
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returningtrue
upon success and throwing anIllegalStateException
if no space is currently available.This implementation returns
true
ifoffer
succeeds, else throws anIllegalStateException
.- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceQueue<E>
- Overrides:
add
in classAbstractCollection<E>
- Parameters:
e
- the element to add- Returns:
true
(as specified byCollection.add(E)
)- Throws:
IllegalStateException
- if the element cannot be added at this time due to capacity restrictionsClassCastException
- if the class of the specified element prevents it from being added to this queueNullPointerException
- if the specified element is null and this queue does not permit null elementsIllegalArgumentException
- if some property of this element prevents it from being added to this queue
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remove
Retrieves and removes the head of this queue. This method differs frompoll
only in that it throws an exception if this queue is empty.This implementation returns the result of
poll
unless the queue is empty.- Specified by:
remove
in interfaceQueue<E>
- Returns:
- the head of this queue
- Throws:
NoSuchElementException
- if this queue is empty
-
element
Retrieves, but does not remove, the head of this queue. This method differs frompeek
only in that it throws an exception if this queue is empty.This implementation returns the result of
peek
unless the queue is empty.- Specified by:
element
in interfaceQueue<E>
- Returns:
- the head of this queue
- Throws:
NoSuchElementException
- if this queue is empty
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clear
public void clear()Removes all of the elements from this queue. The queue will be empty after this call returns.This implementation repeatedly invokes
poll
until it returnsnull
.- Specified by:
clear
in interfaceCollection<E>
- Overrides:
clear
in classAbstractCollection<E>
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addAll
Adds all of the elements in the specified collection to this queue. Attempts to addAll of a queue to itself result inIllegalArgumentException
. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.This implementation iterates over the specified collection, and adds each element returned by the iterator to this queue, in turn. A runtime exception encountered while trying to add an element (including, in particular, a
null
element) may result in only some of the elements having been successfully added when the associated exception is thrown.- Specified by:
addAll
in interfaceCollection<E>
- Overrides:
addAll
in classAbstractCollection<E>
- Parameters:
c
- collection containing elements to be added to this queue- Returns:
true
if this queue changed as a result of the call- Throws:
ClassCastException
- if the class of an element of the specified collection prevents it from being added to this queueNullPointerException
- if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is nullIllegalArgumentException
- if some property of an element of the specified collection prevents it from being added to this queue, or if the specified collection is this queueIllegalStateException
- if not all the elements can be added at this time due to insertion restrictions- See Also:
-