- java.lang.Object
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- java.util.AbstractCollection<E>
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- java.util.AbstractQueue<E>
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- Type Parameters:
E- the type of elements held in this collection
- All Implemented Interfaces:
- Iterable<E>, Collection<E>, Queue<E>
- Direct Known Subclasses:
- ArrayBlockingQueue, ConcurrentLinkedQueue, DelayQueue, LinkedBlockingDeque, LinkedBlockingQueue, LinkedTransferQueue, PriorityBlockingQueue, PriorityQueue, SynchronousQueue
public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E>
This class provides skeletal implementations of someQueueoperations. The implementations in this class are appropriate when the base implementation does not allow null elements. Methodsadd,remove, andelementare based onoffer,poll, andpeek, 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 methodsQueue.peek(),Queue.poll(),Collection.size(), andCollection.iterator(). Typically, additional methods will be overridden as well. If these requirements cannot be met, consider instead subclassingAbstractCollection.This class is a member of the Java Collections Framework.
- Since:
- 1.5
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Constructor Summary
Constructors Modifier Constructor and Description protectedAbstractQueue()Constructor for use by subclasses.
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Method Summary
Methods Modifier and Type Method and Description booleanadd(E e)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.booleanaddAll(Collection<? extends E> c)Adds all of the elements in the specified collection to this queue.voidclear()Removes all of the elements from this queue.Eelement()Retrieves, but does not remove, the head of this queue.Eremove()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
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Method Detail
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add
public boolean add(E e)
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.This implementation returns true if offer succeeds, else throws an IllegalStateException.
- Specified by:
addin interfaceCollection<E>- Specified by:
addin interfaceQueue<E>- Overrides:
addin classAbstractCollection<E>- Parameters:
e- the element to add- Returns:
- true (as specified by
Collection.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
public E remove()
Retrieves and removes the head of this queue. This method differs frompollonly 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:
removein interfaceQueue<E>- Returns:
- the head of this queue
- Throws:
NoSuchElementException- if this queue is empty
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element
public E element()
Retrieves, but does not remove, the head of this queue. This method differs frompeekonly 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:
elementin 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
polluntil it returns null.- Specified by:
clearin interfaceCollection<E>- Overrides:
clearin classAbstractCollection<E>
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addAll
public boolean addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this queue. Attempts to addAll of 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.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:
addAllin interfaceCollection<E>- Overrides:
addAllin 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:
add(Object)
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Document created the 11/06/2005, last modified the 04/03/2020
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