ForwardingQueue (Guava: Google Core Libraries for Java

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

java.lang.Object
  com.google.common.collect.ForwardingObject
      com.google.common.collect.ForwardingCollection<E>
          com.google.common.collect.ForwardingQueue<E>

All Implemented Interfaces:: Iterable<E>, Collection<E>, Queue<E>

Direct Known Subclasses:: ForwardingBlockingQueue

@GwtCompatible public abstract class ForwardingQueue<E>
extends ForwardingCollection<E>
implements Queue<E>
extends ForwardingCollection<E>
implements Queue<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 decorator pattern.

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

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 (imported from Google Collections Library)
Author:: Mike Bostock, Louis Wasserman

Constructor Summary
`protected`	`ForwardingQueue()` Constructor for use by subclasses.

Method Summary
`protected abstract Queue<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 returns `null` if this queue is empty.
`E`	`poll()` Retrieves and removes the head of this queue, or returns `null` if this queue is empty.
`E`	`remove()` Retrieves and removes the head of this queue.
`protected boolean`	`standardOffer(E e)` A sensible definition of `offer(E)` in terms of `ForwardingCollection.add(E)`.
`protected E`	`standardPeek()` A sensible definition of `peek()` in terms of `element()`.
`protected E`	`standardPoll()` A sensible definition of `poll()` in terms of `remove()`.

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.Queue
`add`

Methods inherited from interface java.util.Collection
`addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray`

Constructor Detail

ForwardingQueue

protected ForwardingQueue()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract 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 ForwardingCollection<E>