E
- the type of elements held in this queueIterable<E>
, Collection<E>
, Queue<E>
ArrayBlockingQueue
, ConcurrentLinkedQueue
, DelayQueue
, LinkedBlockingDeque
, LinkedBlockingQueue
, LinkedTransferQueue
, PriorityBlockingQueue
, PriorityQueue
, SynchronousQueue
public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E>
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.
Modifier | Constructor | Description |
---|---|---|
protected |
Constructor for use by subclasses. |
Modifier and Type | Method | Description |
---|---|---|
boolean |
add |
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available. |
boolean |
addAll |
Adds all of the elements in the specified collection to this queue. |
void |
clear() |
Removes all of the elements from this queue. |
E |
element() |
Retrieves, but does not remove, the head of this queue. |
E |
remove() |
Retrieves and removes the head of this queue. |
contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, toArray, toArray, toString
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray
protected AbstractQueue()
public boolean add(E e)
true
upon success and throwing an IllegalStateException
if no space is currently available. This implementation returns true
if offer
succeeds, else throws an IllegalStateException
.
add
in interface Collection<E>
add
in interface Queue<E>
add
in class AbstractCollection<E>
e
- the element to addtrue
(as specified by Collection.add(E)
)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 queuepublic E remove()
poll
only in that it throws an exception if this queue is empty. This implementation returns the result of poll
unless the queue is empty.
remove
in interface Queue<E>
NoSuchElementException
- if this queue is emptypublic E element()
peek
only in that it throws an exception if this queue is empty. This implementation returns the result of peek
unless the queue is empty.
element
in interface Queue<E>
NoSuchElementException
- if this queue is emptypublic void clear()
This implementation repeatedly invokes poll
until it returns null
.
clear
in interface Collection<E>
clear
in class AbstractCollection<E>
public boolean addAll(Collection<? extends E> c)
IllegalArgumentException
. 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.
addAll
in interface Collection<E>
addAll
in class AbstractCollection<E>
c
- collection containing elements to be added to this queuetrue
if this queue changed as a result of the callClassCastException
- 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
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/AbstractQueue.html