- 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 queue
 - 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 allownullelements. Methodsadd,remove, andelementare based onoffer,poll, andpeek, respectively, but throw exceptions instead of indicating failure viafalseornullreturns.A Queueimplementation that extends this class must minimally define a methodQueue.offer(E)which does not permit insertion ofnullelements, 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 SummaryConstructors Modifier Constructor Description protectedAbstractQueue()Constructor for use by subclasses.
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Method SummaryAll Methods Instance Methods Concrete Methods Modifier and Type Method Description booleanadd(E e)Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returningtrueupon success and throwing anIllegalStateExceptionif 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 declared in class java.util.AbstractCollectioncontains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, toArray, toArray, toString
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Methods declared in class java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods declared in interface java.util.Collectioncontains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray
 
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Method Detail- 
addpublic boolean add(E e) Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returningtrueupon success and throwing anIllegalStateExceptionif no space is currently available.This implementation returns trueifoffersucceeds, else throws anIllegalStateException.- Specified by:
- addin interface- Collection<E>
- Specified by:
- addin interface- Queue<E>
- Overrides:
- addin class- AbstractCollection<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 restrictions
- ClassCastException- if the class of the specified element prevents it from being added to this queue
- NullPointerException- if the specified element is null and this queue does not permit null elements
- IllegalArgumentException- if some property of this element prevents it from being added to this queue
 
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removepublic 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 pollunless the queue is empty.- Specified by:
- removein interface- Queue<E>
- Returns:
- the head of this queue
- Throws:
- NoSuchElementException- if this queue is empty
 
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elementpublic 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 peekunless the queue is empty.- Specified by:
- elementin interface- Queue<E>
- Returns:
- the head of this queue
- Throws:
- NoSuchElementException- if this queue is empty
 
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clearpublic 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 returnsnull.- Specified by:
- clearin interface- Collection<E>
- Overrides:
- clearin class- AbstractCollection<E>
 
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addAllpublic 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 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 nullelement) may result in only some of the elements having been successfully added when the associated exception is thrown.- Specified by:
- addAllin interface- Collection<E>
- Overrides:
- addAllin class- AbstractCollection<E>
- Parameters:
- c- collection containing elements to be added to this queue
- Returns:
- trueif 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 queue
- NullPointerException- if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null
- IllegalArgumentException- 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 queue
- IllegalStateException- if not all the elements can be added at this time due to insertion restrictions
- See Also:
- add(Object)
 
 
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