E - the type of elements held in this queueIterable<E>, Collection<E>, BlockingQueue<E>, Queue<E>
public class DelayQueue<E extends Delayed> extends AbstractQueue<E> implements BlockingQueue<E>
Delayed elements, in which an element generally becomes eligible for removal when its delay has expired.
While this class implements the BlockingQueue interface, it intentionally violates the general contract of BlockingQueue, in that the following methods disregard the presence of unexpired elements and only ever remove the expired head:
All other methods operate on both expired and unexpired elements. For example, the size() method returns the count of all elements. Method peek() may return the (non-null) head even when take() would block waiting for that element to expire.
This queue does not permit null elements.
This class and its iterator implement all of the optional methods of the Collection and Iterator interfaces. The Iterator provided in method iterator() is not guaranteed to traverse the elements of the DelayQueue in any particular order.
This class is a member of the Java Collections Framework.
| Constructor | Description |
|---|---|
DelayQueue() |
Creates a new DelayQueue that is initially empty. |
DelayQueue |
Creates a DelayQueue initially containing the elements of the given collection of Delayed instances. |
| Modifier and Type | Method | Description |
|---|---|---|
boolean |
add |
Inserts the specified element into this delay queue. |
void |
clear() |
Atomically removes all of the elements from this delay queue. |
int |
drainTo |
Removes all available elements from this queue and adds them to the given collection. |
int |
drainTo |
Removes at most the given number of available elements from this queue and adds them to the given collection. |
Iterator |
iterator() |
Returns an iterator over all the elements (both expired and unexpired) in this queue. |
boolean |
offer |
Inserts the specified element into this delay queue. |
boolean |
offer |
Inserts the specified element into this delay queue. |
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 expired head of this queue, or returns null if this queue has no expired elements. |
E |
poll |
Retrieves and removes the expired head of this queue, waiting if necessary until an expired element is available on this queue, or the specified wait time expires. |
void |
put |
Inserts the specified element into this delay queue. |
int |
remainingCapacity() |
Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained. |
E |
remove() |
Retrieves and removes the expired head of this queue, or throws an exception if this queue has no expired elements. |
boolean |
remove |
Removes a single instance of the specified element from this queue, if it is present, whether or not it has expired. |
int |
size() |
Returns the number of elements in this collection. |
E |
take() |
Retrieves and removes the expired head of this queue, waiting if necessary until an expired element is available on this queue. |
Object[] |
toArray() |
Returns an array containing all of the elements in this queue. |
<T> T[] |
toArray |
Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array. |
addAll, element
contains, containsAll, isEmpty, removeAll, retainAll, toString
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
contains
addAll, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray
public DelayQueue()
DelayQueue that is initially empty.public DelayQueue(Collection<? extends E> c)
DelayQueue initially containing the elements of the given collection of Delayed instances.c - the collection of elements to initially containNullPointerException - if the specified collection or any of its elements are nullpublic boolean add(E e)
add in interface BlockingQueue<E extends Delayed>
add in interface Collection<E extends Delayed>
add in interface Queue<E extends Delayed>
add in class AbstractQueue<E extends Delayed>
e - the element to addtrue (as specified by Collection.add(E))NullPointerException - if the specified element is nullpublic boolean offer(E e)
offer in interface BlockingQueue<E extends Delayed>
offer in interface Queue<E extends Delayed>
e - the element to addtrueNullPointerException - if the specified element is nullpublic void put(E e)
put in interface BlockingQueue<E extends Delayed>
e - the element to addNullPointerException - if the specified element is nullpublic boolean offer(E e, long timeout, TimeUnit unit)
offer in interface BlockingQueue<E extends Delayed>
e - the element to addtimeout - This parameter is ignored as the method never blocksunit - This parameter is ignored as the method never blockstrueNullPointerException - if the specified element is nullpublic E poll()
null if this queue has no expired elements.public E take() throws InterruptedException
take in interface BlockingQueue<E extends Delayed>
InterruptedException - if interrupted while waitingpublic E poll(long timeout, TimeUnit unit) throws InterruptedException
poll in interface BlockingQueue<E extends Delayed>
timeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parameternull if the specified waiting time elapses before an element with an expired delay becomes availableInterruptedException - if interrupted while waitingpublic E remove()
remove in interface Queue<E extends Delayed>
remove in class AbstractQueue<E extends Delayed>
NoSuchElementException - if this queue has no elements with an expired delaypublic E peek()
null if this queue is empty. Unlike poll, if no expired elements are available in the queue, this method returns the element that will expire next, if one exists.public int size()
CollectionInteger.MAX_VALUE elements, returns Integer.MAX_VALUE.size in interface Collection<E extends Delayed>
public int drainTo(Collection<? super E> c)
BlockingQueuec 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.drainTo in interface BlockingQueue<E extends Delayed>
c - the collection to transfer elements intoUnsupportedOperationException - if addition of elements is not supported by the specified collectionClassCastException - if the class of an element of this queue prevents it from being added to the specified collectionNullPointerException - if the specified collection is nullIllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collectionpublic int drainTo(Collection<? super E> c, int maxElements)
BlockingQueuec 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.drainTo in interface BlockingQueue<E extends Delayed>
c - the collection to transfer elements intomaxElements - the maximum number of elements to transferUnsupportedOperationException - if addition of elements is not supported by the specified collectionClassCastException - if the class of an element of this queue prevents it from being added to the specified collectionNullPointerException - if the specified collection is nullIllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collectionpublic void clear()
clear in interface Collection<E extends Delayed>
clear in class AbstractQueue<E extends Delayed>
public int remainingCapacity()
Integer.MAX_VALUE because a DelayQueue is not capacity constrained.remainingCapacity in interface BlockingQueue<E extends Delayed>
Integer.MAX_VALUEpublic Object[] toArray()
The returned array will be "safe" in that no references to it are maintained by this queue. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
toArray in interface Collection<E extends Delayed>
toArray in class AbstractCollection<E extends Delayed>
public <T> T[] toArray(T[] a)
If this queue fits in the specified array with room to spare (i.e., the array has more elements than this queue), the element in the array immediately following the end of the queue is set to null.
Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.
The following code can be used to dump a delay queue into a newly allocated array of Delayed:
Delayed[] a = q.toArray(new Delayed[0]); Note that toArray(new Object[0]) is identical in function to toArray().toArray in interface Collection<E extends Delayed>
toArray in class AbstractCollection<E extends Delayed>
T - the component type of the array to contain the collectiona - the array into which the elements of the queue are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purposeArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this queueNullPointerException - if the specified array is nullpublic boolean remove(Object o)
remove in interface BlockingQueue<E extends Delayed>
remove in interface Collection<E extends Delayed>
remove in class AbstractCollection<E extends Delayed>
o - element to be removed from this collection, if presenttrue if an element was removed as a result of this callpublic Iterator<E> iterator()
The returned iterator is weakly consistent.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/concurrent/DelayQueue.html