java.util.concurrent.DelayQueue<E extends java.util.concurrent.Delayed>

DelayQueue<E>

Java SE 6

Extends: AbstractCollection > AbstractQueue

An unbounded blocking queue of Delayed elements, in which an element can only be taken when its delay has expired. The head of the queue is that Delayed element whose delay expired furthest in the past. If no delay has expired there is no head and poll will return null. Expiration occurs when an element's getDelay(TimeUnit.NANOSECONDS) method returns a value less than or equal to zero. Even though unexpired elements cannot be removed using take or poll, they are otherwise treated as normal elements. For example, the size method returns the count of both expired and unexpired elements. This queue does not permit null elements.

This class and its iterator implement all of the optional methods of the Collection and Iterator interfaces.

This class is a member of the Java Collections Framework.

since 1.5

E the type of elements held in this collection

Constructors

public

DelayQueue()
Creates a new DelayQueue that is initially empty.

public

DelayQueue(Collection c)
Creates a DelayQueue initially containing the elements of the given collection of Delayed instances.

c	the collection of elements to initially contain
Throws	NullPointerException: if the specified collection or any of its elements are null

Methods

public boolean

add(Delayed e)
Inserts the specified element into this delay queue.

e	the element to add
return	`true` (as specified by `Collection#add`)
Throws	NullPointerException: als het gespecifieerde element null is

public void

clear()
Atomically removes all of the elements from this delay queue. The queue will be empty after this call returns. Elements with an unexpired delay are not waited for; they are simply discarded from the queue.

public int

drainTo(Collection c)

Throws	UnsupportedOperationException: if addition of elements is not supported by the specified collection
Throws	ClassCastException: if the class of an element of this queue prevents it from being added to the specified collection
Throws	NullPointerException: if the specified collection is null
Throws	IllegalArgumentException: if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

public int

drainTo(Collection c, int maxElements)

Throws	UnsupportedOperationException: if addition of elements is not supported by the specified collection
Throws	ClassCastException: if the class of an element of this queue prevents it from being added to the specified collection
Throws	NullPointerException: if the specified collection is null
Throws	IllegalArgumentException: if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

public Iterator

iterator()
Returns an iterator over all the elements (both expired and unexpired) in this queue. The iterator does not return the elements in any particular order. The returned Iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

return

an iterator over the elements in this queue

public boolean

offer(Delayed e)
Inserts the specified element into this delay queue.

e	the element to add
return	`true`
Throws	NullPointerException: als het gespecifieerde element null is

public boolean

offer(Delayed e, long timeout, TimeUnit unit)
Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

e	the element to add
timeout	This parameter is ignored as the method never blocks
unit	This parameter is ignored as the method never blocks
return	`true`
Throws	NullPointerException: als het gespecifieerde element null is

public Delayed

peek()
Retrieves, but does not remove, the head of this queue, or returns 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.

return the head of this queue, or null if this queue is empty.

public Delayed

poll()
Retrieves and removes the head of this queue, or returns null if this queue has no elements with an expired delay.

return the head of this queue, or null if this queue has no elements with an expired delay

public Delayed

poll(long timeout, TimeUnit unit) throws InterruptedException
Retrieves and removes the head of this queue, waiting if necessary until an element with an expired delay is available on this queue, or the specified wait time expires.

return	the head of this queue, or `null` if the specified waiting time elapses before an element with an expired delay becomes available
Throws	InterruptedException: if interrupted while waiting

public void

put(Delayed e)
Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

e	the element to add
Throws	NullPointerException: als het gespecifieerde element null is

public int

remainingCapacity()
Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.

return Integer.MAX_VALUE

public boolean

remove(Object o)
Removes a single instance of the specified element from this queue, if it is present, whether or not it has expired.

public int

size()

public Delayed

take() throws InterruptedException
Retrieves and removes the head of this queue, waiting if necessary until an element with an expired delay is available on this queue.

return	the head of this queue
Throws	InterruptedException: if interrupted while waiting

public Object[]

toArray()
Returns an array containing all of the elements in this queue. The returned array elements are in no particular order.

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.

return an array containing all of the elements in this queue

public Object[]<T>

toArray(Object[] a)
Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array. The returned array elements are in no particular order. If the queue fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this queue.

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().

a	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 purpose
return	an array containing all of the elements in this queue
Throws	ArrayStoreException: if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue
Throws	NullPointerException: if the specified array is null

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Java SE 6