Class EvictingQueue<E>

java.lang.Object

com.google.common.collect.ForwardingObject

com.google.common.collect.ForwardingCollection<E>

com.google.common.collect.ForwardingQueue<E>

com.google.common.collect.EvictingQueue<E>

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, Queue<E>

@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

Method Summary

Modifier and Type	Method	Description
boolean	add(E e)	Adds the given element to this queue.
boolean	addAll(Collection<? extends E> collection)
static <E> EvictingQueue<E>	create(int maxSize)	Creates and returns a new evicting queue that will hold up to maxSize 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()

Methods inherited from class com.google.common.collect.ForwardingQueue

element, peek, poll, remove, standardOffer, standardPeek, standardPoll

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

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

clear, contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray

Methods inherited from interface java.lang.Iterable

forEach

Method Details

create

public static <E> EvictingQueue<E> create(int maxSize)

Creates and returns a new evicting queue that will hold up to maxSize elements.

When maxSize is zero, elements will be evicted immediately after being added to the queue.

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

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 as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

Specified by:

delegate in class ForwardingQueue<E>

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.

Specified by:

offer in interface Queue<E>

Overrides:

offer in class ForwardingQueue<E>

Returns:

true always

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 interface Collection<E>

Specified by:

add in interface Queue<E>

Overrides:

add in class ForwardingCollection<E>

Returns:

true always

addAll

@CanIgnoreReturnValue
public boolean addAll(Collection<? extends E> collection)

Specified by:

addAll in interface Collection<E>

Overrides:

addAll in class ForwardingCollection<E>

toArray

public Object[] toArray()

Specified by:

toArray in interface Collection<E>

Overrides:

toArray in class ForwardingCollection<E>