@GwtCompatible public abstract class ForwardingQueue<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.
| 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() |
boolean |
offer(E o) |
E |
peek() |
E |
poll() |
E |
remove() |
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, toArraytoStringclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitaddAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArrayprotected abstract Queue<E> delegate()
ForwardingObjectReturns 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.
delegate in class ForwardingCollection<E>protected boolean standardOffer(E e)
A sensible definition of 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()
A sensible definition of peek() in terms of element(). If you override element(), you may wish to override peek() to forward to this implementation.