Package com.google.common.collect
Class ForwardingQueue<E>
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- com.google.common.collect.ForwardingObject
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- com.google.common.collect.ForwardingCollection<E>
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- com.google.common.collect.ForwardingQueue<E>
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- All Implemented Interfaces:
<E>
,<E>
,<E>
- Direct Known Subclasses:
EvictingQueue
,ForwardingBlockingQueue
,ForwardingDeque
@GwtCompatible public abstract class ForwardingQueue<E> extends ForwardingCollection<E> implements <E>
A queue which forwards all its method calls to another queue. Subclasses should override one or more methods to modify the behavior of the backing queue as desired per the .Warning: The methods of
ForwardingQueue
forward indiscriminately to the methods of the delegate. For example, overridingForwardingCollection.add(E)
alone will not change the behavior ofoffer(E)
which can lead to unexpected behavior. In this case, you should overrideoffer
as well, either providing your own implementation, or delegating to the providedstandardOffer
method.default
method warning: This class does not forward calls todefault
methods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on theForwardingQueue
.The
standard
methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.- Since:
- 2.0
- Author:
- Mike Bostock, Louis Wasserman
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Constructor Summary
Constructors Modifier Constructor Description protected
ForwardingQueue()
Constructor for use by subclasses.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected abstract <E>
delegate()
Returns the backing delegate instance that methods are forwarded to.E
element()
Retrieves, but does not remove, the head of this queue.boolean
offer(E o)
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions.E
peek()
Retrieves, but does not remove, the head of this queue, or returnsnull
if this queue is empty.E
poll()
Retrieves and removes the head of this queue, or returnsnull
if this queue is empty.E
remove()
Retrieves and removes the head of this queue.protected boolean
standardOffer(E e)
A sensible definition ofoffer(E)
in terms ofForwardingCollection.add(E)
.protected E
standardPeek()
protected E
standardPoll()
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Methods inherited from class com.google.common.collect.ForwardingCollection
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, standardAddAll, standardClear, standardContains, standardContainsAll, standardIsEmpty, standardRemove, standardRemoveAll, standardRetainAll, standardToArray, standardToArray, standardToString, toArray, toArray
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Methods inherited from class com.google.common.collect.ForwardingObject
toString
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Constructor Detail
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ForwardingQueue
protected ForwardingQueue()
Constructor for use by subclasses.
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Method Detail
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delegate
protected abstract <E> delegate()
Description copied from class:ForwardingObject
Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such asForwardingSet.delegate()
. Concrete subclasses override this method to supply the instance being decorated.- Specified by:
delegate
in classForwardingCollection<E>
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offer
public boolean offer(E o)
Description copied from interface:Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions. When using a capacity-restricted queue, this method is generally preferable to , which can fail to insert an element only by throwing an exception.- Specified by:
in interface
<E>
- Parameters:
o
- the element to add- Returns:
true
if the element was added to this queue, elsefalse
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poll
public E poll()
Description copied from interface:Retrieves and removes the head of this queue, or returnsnull
if this queue is empty.- Specified by:
in interface
<E>
- Returns:
- the head of this queue, or
null
if this queue is empty
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remove
public E remove()
Description copied from interface:Retrieves and removes the head of this queue. This method differs from only in that it throws an exception if this queue is empty.- Specified by:
in interface
<E>
- Returns:
- the head of this queue
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peek
public E peek()
Description copied from interface:Retrieves, but does not remove, the head of this queue, or returnsnull
if this queue is empty.- Specified by:
in interface
<E>
- Returns:
- the head of this queue, or
null
if this queue is empty
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element
public E element()
Description copied from interface:Retrieves, but does not remove, the head of this queue. This method differs from only in that it throws an exception if this queue is empty.- Specified by:
in interface
<E>
- Returns:
- the head of this queue
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standardOffer
protected boolean standardOffer(E e)
A sensible definition ofoffer(E)
in terms ofForwardingCollection.add(E)
. If you overrideForwardingCollection.add(E)
, you may wish to overrideoffer(E)
to forward to this implementation.- Since:
- 7.0
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standardPeek
protected E standardPeek()
A sensible definition ofpeek()
in terms ofelement()
. If you overrideelement()
, you may wish to overridepeek()
to forward to this implementation.- Since:
- 7.0
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