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.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/AbstractQueue.html