@GwtCompatible public abstract class ForwardingQueue<E> extends ForwardingCollection<E> implements Queue<E>
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.
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 ForwardingQueue
.
The standard
methods are not guaranteed to be thread-safe, even when all of the
methods that they depend on are thread-safe.
Modifier | Constructor and Description |
---|---|
protected |
ForwardingQueue()
Constructor for use by subclasses.
|
Modifier and Type | Method and Description |
---|---|
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()
|
protected E |
standardPoll()
|
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, standardAddAll, standardClear, standardContains, standardContainsAll, standardIsEmpty, standardRemove, standardRemoveAll, standardRetainAll, standardToArray, standardToArray, standardToString, toArray, toArray
toString
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray
protected ForwardingQueue()
protected abstract Queue<E> delegate()
ForwardingObject
ForwardingSet.delegate()
. Concrete subclasses override this method to supply the
instance being decorated.delegate
in class ForwardingCollection<E>
@CanIgnoreReturnValue public boolean offer(E o)
java.util.Queue
Queue.add(E)
, which can fail to insert an element only
by throwing an exception.@CanIgnoreReturnValue public E poll()
java.util.Queue
null
if this queue is empty.@CanIgnoreReturnValue public E remove()
java.util.Queue
poll
only in that it throws an exception if this
queue is empty.public E peek()
java.util.Queue
null
if this queue is empty.public E element()
java.util.Queue
peek
only in that it throws an exception
if this queue is empty.protected boolean standardOffer(E e)
offer(E)
in terms of ForwardingCollection.add(E)
. If you override ForwardingCollection.add(E)
,
you may wish to override offer(E)
to forward to this implementation.protected E standardPeek()
peek()
in terms of element()
. If you override element()
, you may wish to override peek()
to forward to this implementation.Copyright © 2010–2019. All rights reserved.