Package com.google.common.collect
Class EvictingQueue<E>
- java.lang.Object
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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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- com.google.common.collect.EvictingQueue<E>
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- All Implemented Interfaces:
Serializable
,Iterable<E>
,Collection<E>
,Queue<E>
@Beta @GwtCompatible public final class EvictingQueue<E> extends ForwardingQueue<E> implements Serializable
A non-blocking queue which automatically evicts elements from the head of the queue when attempting to add new elements onto the queue and it is full. This queue orders elements FIFO (first-in-first-out). This data structure is logically equivalent to a circular buffer (i.e., cyclic buffer or ring buffer).An evicting queue must be configured with a maximum size. Each time an element is added to a full queue, the queue automatically removes its head element. This is different from conventional bounded queues, which either block or reject new elements when full.
This class is not thread-safe, and does not accept null elements.
- Since:
- 15.0
- Author:
- Kurt Alfred Kluever
- See Also:
- Serialized Form
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
add(E e)
Adds the given element to this queue.boolean
addAll(Collection<? extends E> collection)
Adds all of the elements in the specified collection to this collection (optional operation).static <E> EvictingQueue<E>
create(int maxSize)
Creates and returns a new evicting queue that will hold up tomaxSize
elements.protected Queue<E>
delegate()
Returns the backing delegate instance that methods are forwarded to.boolean
offer(E e)
Adds the given element to this queue.int
remainingCapacity()
Returns the number of additional elements that this queue can accept without evicting; zero if the queue is currently full.Object[]
toArray()
Returns an array containing all of the elements in this collection.-
Methods inherited from class com.google.common.collect.ForwardingQueue
element, peek, poll, remove, standardOffer, standardPeek, standardPoll
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Methods inherited from class com.google.common.collect.ForwardingCollection
clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, standardAddAll, standardClear, standardContains, standardContainsAll, standardIsEmpty, standardRemove, standardRemoveAll, standardRetainAll, standardToArray, standardToArray, standardToString, toArray
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Methods inherited from class com.google.common.collect.ForwardingObject
toString
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface java.util.Collection
clear, contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray
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Method Detail
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create
public static <E> EvictingQueue<E> create(int maxSize)
Creates and returns a new evicting queue that will hold up tomaxSize
elements.When
maxSize
is zero, elements will be evicted immediately after being added to the queue.
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remainingCapacity
public int remainingCapacity()
Returns the number of additional elements that this queue can accept without evicting; zero if the queue is currently full.- Since:
- 16.0
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delegate
protected Queue<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 classForwardingQueue<E>
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offer
@CanIgnoreReturnValue public boolean offer(E e)
Adds the given element to this queue. If the queue is currently full, the element at the head of the queue is evicted to make room.
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add
@CanIgnoreReturnValue public boolean add(E e)
Adds the given element to this queue. If the queue is currently full, the element at the head of the queue is evicted to make room.- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceQueue<E>
- Overrides:
add
in classForwardingCollection<E>
- Parameters:
e
- element whose presence in this collection is to be ensured- Returns:
true
always
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addAll
@CanIgnoreReturnValue public boolean addAll(Collection<? extends E> collection)
Description copied from interface:java.util.Collection
Adds all of the elements in the specified collection to this collection (optional operation). The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this collection, and this collection is nonempty.)- Specified by:
addAll
in interfaceCollection<E>
- Overrides:
addAll
in classForwardingCollection<E>
- Parameters:
collection
- collection containing elements to be added to this collection- Returns:
true
if this collection changed as a result of the call- See Also:
Collection.add(Object)
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toArray
public Object[] toArray()
Description copied from interface:java.util.Collection
Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array's runtime component type isObject
.The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array.
- Specified by:
toArray
in interfaceCollection<E>
- Overrides:
toArray
in classForwardingCollection<E>
- Returns:
- an array, whose runtime component
type is
Object
, containing all of the elements in this collection
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