Package com.google.common.util.concurrent

Class ForwardingBlockingDeque<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.ForwardingDeque<E>

com.google.common.util.concurrent.ForwardingBlockingDeque<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>, BlockingDeque<E>, BlockingQueue<E>, Deque<E>, Queue<E>

@GwtIncompatible
public abstract class ForwardingBlockingDeque<E>
extends ForwardingDeque<E>
implements BlockingDeque<E>

A BlockingDeque which forwards all its method calls to another BlockingDeque. Subclasses should override one or more methods to modify the behavior of the backing deque as desired per the decorator pattern.

Warning: The methods of ForwardingBlockingDeque forward indiscriminately to the methods of the delegate. For example, overriding ForwardingCollection.add(E) alone will not change the behaviour of offer(E, long, java.util.concurrent.TimeUnit) which can lead to unexpected behaviour. In this case, you should override offer as well, either providing your own implementation, or delegating to the provided standardOffer method.

default method warning: This class does not forward calls to default methods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on the ForwardingBlockingDeque.

The standard methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.

Since:

21.0 (since 14.0 as ForwardingBlockingDeque)

Author:

Emily Soldal

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ForwardingBlockingDeque()	Constructor for use by subclasses.

Method Summary

Modifier and Type	Method	Description
protected abstract BlockingDeque<E>	delegate()	Returns the backing delegate instance that methods are forwarded to.
int	drainTo(Collection<? super E> c)	Removes all available elements from this queue and adds them to the given collection.
int	drainTo(Collection<? super E> c, int maxElements)	Removes at most the given number of available elements from this queue and adds them to the given collection.
boolean	offer(E e, long timeout, TimeUnit unit)	Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available.
boolean	offerFirst(E e, long timeout, TimeUnit unit)	Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.
boolean	offerLast(E e, long timeout, TimeUnit unit)	Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.
E	poll(long timeout, TimeUnit unit)	Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available.
E	pollFirst(long timeout, TimeUnit unit)	Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.
E	pollLast(long timeout, TimeUnit unit)	Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.
void	put(E e)	Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.
void	putFirst(E e)	Inserts the specified element at the front of this deque, waiting if necessary for space to become available.
void	putLast(E e)	Inserts the specified element at the end of this deque, waiting if necessary for space to become available.
int	remainingCapacity()	Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking, or Integer.MAX_VALUE if there is no intrinsic limit.
E	take()	Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available.
E	takeFirst()	Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.
E	takeLast()	Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.

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

addFirst, addLast, descendingIterator, getFirst, getLast, offerFirst, offerLast, peekFirst, peekLast, pollFirst, pollLast, pop, push, removeFirst, removeFirstOccurrence, removeLast, removeLastOccurrence

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

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

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

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.concurrent.BlockingDeque

add, addFirst, addLast, contains, element, iterator, offer, offerFirst, offerLast, peek, poll, push, remove, remove, removeFirstOccurrence, removeLastOccurrence, size

Methods inherited from interface java.util.Collection

clear, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArray

Methods inherited from interface java.util.Deque

add, addAll, contains, descendingIterator, getFirst, getLast, offer, peekFirst, peekLast, pollFirst, pollLast, pop, remove, removeFirst, removeLast

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

ForwardingBlockingDeque

protected ForwardingBlockingDeque()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract BlockingDeque<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 ForwardingDeque<E>

remainingCapacity

public int remainingCapacity()

Description copied from interface: java.util.concurrent.BlockingQueue

Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking, or Integer.MAX_VALUE if there is no intrinsic limit.

Note that you cannot always tell if an attempt to insert an element will succeed by inspecting remainingCapacity because it may be the case that another thread is about to insert or remove an element.

Specified by:

remainingCapacity in interface BlockingQueue<E>

Returns:

the remaining capacity

putFirst

public void putFirst(E e)
              throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Inserts the specified element at the front of this deque, waiting if necessary for space to become available.

Specified by:

putFirst in interface BlockingDeque<E>

Parameters:

e - the element to add

Throws:

InterruptedException - if interrupted while waiting

putLast

public void putLast(E e)
             throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Inserts the specified element at the end of this deque, waiting if necessary for space to become available.

Specified by:

putLast in interface BlockingDeque<E>

Parameters:

e - the element to add

Throws:

InterruptedException - if interrupted while waiting

offerFirst

public boolean offerFirst(E e,
                          long timeout,
                          TimeUnit unit)
                   throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.

Specified by:

offerFirst in interface BlockingDeque<E>

Parameters:

e - the element to add

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

Returns:

true if successful, or false if the specified waiting time elapses before space is available

Throws:

InterruptedException - if interrupted while waiting

offerLast

public boolean offerLast(E e,
                         long timeout,
                         TimeUnit unit)
                  throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.

Specified by:

offerLast in interface BlockingDeque<E>

Parameters:

e - the element to add

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

Returns:

true if successful, or false if the specified waiting time elapses before space is available

Throws:

InterruptedException - if interrupted while waiting

takeFirst

public E takeFirst()
            throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.

Specified by:

takeFirst in interface BlockingDeque<E>

Returns:

the head of this deque

Throws:

InterruptedException - if interrupted while waiting

takeLast

public E takeLast()
           throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.

Specified by:

takeLast in interface BlockingDeque<E>

Returns:

the tail of this deque

Throws:

InterruptedException - if interrupted while waiting

pollFirst

public E pollFirst(long timeout,
                   TimeUnit unit)
            throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.

Specified by:

pollFirst in interface BlockingDeque<E>

Parameters:

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

Returns:

the head of this deque, or null if the specified waiting time elapses before an element is available

Throws:

InterruptedException - if interrupted while waiting

pollLast

public E pollLast(long timeout,
                  TimeUnit unit)
           throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.

Specified by:

pollLast in interface BlockingDeque<E>

Parameters:

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

Returns:

the tail of this deque, or null if the specified waiting time elapses before an element is available

Throws:

InterruptedException - if interrupted while waiting

put

public void put(E e)
         throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.

This method is equivalent to putLast.

Specified by:

put in interface BlockingDeque<E>

Specified by:

put in interface BlockingQueue<E>

Parameters:

e - the element to add

Throws:

InterruptedException - if interrupted while waiting

offer

public boolean offer(E e,
                     long timeout,
                     TimeUnit unit)
              throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available.

This method is equivalent to offerLast.

Specified by:

offer in interface BlockingDeque<E>

Specified by:

offer in interface BlockingQueue<E>

Parameters:

e - the element to add

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

Returns:

true if the element was added to this deque, else false

Throws:

InterruptedException - if interrupted while waiting

take

public E take()
       throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available.

This method is equivalent to takeFirst.

Specified by:

take in interface BlockingDeque<E>

Specified by:

take in interface BlockingQueue<E>

Returns:

the head of this deque

Throws:

InterruptedException - if interrupted while waiting

poll

public E poll(long timeout,
              TimeUnit unit)
       throws InterruptedException

Description copied from interface: java.util.concurrent.BlockingDeque

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available.

This method is equivalent to pollFirst.

Specified by:

poll in interface BlockingDeque<E>

Specified by:

poll in interface BlockingQueue<E>

Parameters:

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

Returns:

the head of this deque, or null if the specified waiting time elapses before an element is available

Throws:

InterruptedException - if interrupted while waiting

drainTo

public int drainTo(Collection<? super E> c)

Description copied from interface: java.util.concurrent.BlockingQueue

Removes all available elements from this queue and adds them to the given collection. This operation may be more efficient than repeatedly polling this queue. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain 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.

Specified by:

drainTo in interface BlockingQueue<E>

Parameters:

c - the collection to transfer elements into

Returns:

the number of elements transferred

drainTo

public int drainTo(Collection<? super E> c,
                   int maxElements)

Description copied from interface: java.util.concurrent.BlockingQueue

Removes at most the given number of available elements from this queue and adds them to the given collection. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain 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.

Specified by:

drainTo in interface BlockingQueue<E>

Parameters:

c - the collection to transfer elements into

maxElements - the maximum number of elements to transfer

Returns:

the number of elements transferred