Added in API level 1

DelayQueue

open class DelayQueue<E : Delayed!> : AbstractQueue<E>, BlockingQueue<E>

kotlin.Any
↳	java.util.AbstractCollection<E>
	↳	java.util.AbstractQueue<E>
		↳	java.util.concurrent.DelayQueue

An unbounded blocking queue of Delayed elements, in which an element generally becomes eligible for removal when its delay has expired.

An element is considered expired when its getDelay(TimeUnit.NANOSECONDS) method would return a value less than or equal to zero.

An element is considered the head of the queue if it is the element with the earliest expiration time, whether in the past or the future, if there is such an element.

An element is considered the expired head of the queue if it is the expired element with the earliest expiration time in the past, if there is such an element. The expired head, when present, is also the head.

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:

• poll()
• poll(long,java.util.concurrent.TimeUnit)
• take()
• remove()

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.

Summary

Public constructors
DelayQueue() Creates a new DelayQueue that is initially empty.
DelayQueue(c: MutableCollection<out E>!) Creates a DelayQueue initially containing the elements of the given collection of Delayed instances.

Public methods
open Boolean	add(element: E) Inserts the specified element into this delay queue.
open Unit	clear() Atomically removes all of the elements from this delay queue.
open Int	drainTo(c: MutableCollection<in E>!)
open Int	drainTo(c: MutableCollection<in E>!, maxElements: Int)
open MutableIterator<E>	iterator() Returns an iterator over all the elements (both expired and unexpired) in this queue.
open Boolean	offer(e: E) Inserts the specified element into this delay queue.
open Boolean	offer(e: E, timeout: Long, unit: TimeUnit!) Inserts the specified element into this delay queue.
open E?	peek() Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
open E?	poll() Retrieves and removes the expired head of this queue, or returns null if this queue has no expired elements.
open E	poll(timeout: Long, unit: TimeUnit!) 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.
open Unit	put(e: E) Inserts the specified element into this delay queue.
open Int	remainingCapacity() Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.
open E	remove() Retrieves and removes the expired head of this queue, or throws an exception if this queue has no expired elements.
open Boolean	remove(element: E?) Removes a single instance of the specified element from this queue, if it is present, whether or not it has expired.
open E	take() Retrieves and removes the expired head of this queue, waiting if necessary until an expired element is available on this queue.
open Array<Any!>	toArray() Returns an array containing all of the elements in this queue.
open Array<T>	toArray(a: Array<T>) Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array.

Inherited functions
From class AbstractQueue Boolean addAll(elements: Collection<E>) Adds all of the elements in the specified collection to this queue. Attempts to addAll of 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. This implementation iterates over the specified collection, and adds each element returned by the iterator to this queue, in turn. A runtime exception encountered while trying to add an element (including, in particular, a null element) may result in only some of the elements having been successfully added when the associated exception is thrown. E element() Retrieves, but does not remove, the head of this queue. This method differs from peek only in that it throws an exception if this queue is empty. This implementation returns the result of peek unless the queue is empty.
From class AbstractCollection Boolean contains(element: E?) Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that Objects.equals(o, e). Boolean containsAll(elements: Collection<E>) Returns true if this collection contains all of the elements in the specified collection. Boolean isEmpty() Returns true if this collection contains no elements. MutableIterator<E> iterator() Returns an iterator over the elements contained in this collection. Boolean remove(element: E?) Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element e such that Objects.equals(o, e), if this collection contains one or more such elements. Returns true if this collection contained the specified element (or equivalently, if this collection changed as a result of the call). Boolean removeAll(elements: Collection<E>) Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection. Boolean retainAll(elements: Collection<E>) Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection. Array<Any!> toArray() Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array's runtime component type is Object. The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array. Array<T> toArray(a: Array<T>) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection 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 collection. If this collection fits in the specified array with room to spare (i.e., the array has more elements than this collection), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of this collection only if the caller knows that this collection does not contain any null elements.) If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. String toString() Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String.valueOf(Object).
From class Queue Boolean offer(e: E) Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions. When using a capacity-restricted queue, this method is generally preferable to add, which can fail to insert an element only by throwing an exception. 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.

Properties
open Int	size

Inherited properties
From class AbstractCollection Int size

Public constructors

DelayQueue

Added in API level 1

DelayQueue()

Creates a new DelayQueue that is initially empty.

DelayQueue

Added in API level 1

DelayQueue(c: MutableCollection<out E>!)

Creates a DelayQueue initially containing the elements of the given collection of Delayed instances.

Parameters
c	MutableCollection<out E>!: the collection of elements to initially contain

Exceptions
java.lang.NullPointerException	if the specified collection or any of its elements are null

Public methods

add

Added in API level 1

open fun add(element: E): Boolean

Inserts the specified element into this delay queue.

Parameters
e	the element to add

Return
Boolean	true (as specified by Collection.add)

Exceptions
java.lang.UnsupportedOperationException	if the add operation is not supported by this collection
java.lang.ClassCastException	if the class of the specified element prevents it from being added to this queue
java.lang.NullPointerException	if the specified element is null
java.lang.IllegalArgumentException	if some property of the specified element prevents it from being added to this queue
java.lang.IllegalStateException	if the element cannot be added at this time due to capacity restrictions

clear

Added in API level 1

open fun clear(): Unit

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.

Exceptions
java.lang.UnsupportedOperationException	if the clear operation is not supported by this collection

drainTo

Added in API level 1

open fun drainTo(c: MutableCollection<in E>!): Int

Parameters
c	MutableCollection<in E>!: the collection to transfer elements into

Return
Int	the number of elements transferred

Exceptions
java.lang.UnsupportedOperationException	if addition of elements is not supported by the specified collection
java.lang.ClassCastException	if the class of an element of this queue prevents it from being added to the specified collection
java.lang.NullPointerException	if the specified collection is null
java.lang.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

drainTo

Added in API level 1

open fun drainTo(
    c: MutableCollection<in E>!, 
    maxElements: Int
): Int

Parameters
c	MutableCollection<in E>!: the collection to transfer elements into
maxElements	Int: the maximum number of elements to transfer

Return
Int	the number of elements transferred

Exceptions
java.lang.UnsupportedOperationException	if addition of elements is not supported by the specified collection
java.lang.ClassCastException	if the class of an element of this queue prevents it from being added to the specified collection
java.lang.NullPointerException	if the specified collection is null
java.lang.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

iterator

Added in API level 1

open fun iterator(): MutableIterator<E>

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 weakly consistent.

Return
MutableIterator<E>	an iterator over the elements in this queue

offer

Added in API level 1

open fun offer(e: E): Boolean

Inserts the specified element into this delay queue.

Parameters
e	E: the element to add

Return
Boolean	true

Exceptions
java.lang.ClassCastException	if the class of the specified element prevents it from being added to this queue
java.lang.NullPointerException	if the specified element is null
java.lang.IllegalArgumentException	if some property of the specified element prevents it from being added to this queue

offer

Added in API level 1

open fun offer(
    e: E, 
    timeout: Long, 
    unit: TimeUnit!
): Boolean

Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

Parameters
e	E: the element to add
timeout	Long: This parameter is ignored as the method never blocks
unit	TimeUnit!: This parameter is ignored as the method never blocks

Return
Boolean	true

Exceptions
java.lang.InterruptedException	if interrupted while waiting
java.lang.ClassCastException	if the class of the specified element prevents it from being added to this queue
java.lang.NullPointerException	if the specified element is null
java.lang.IllegalArgumentException	if some property of the specified element prevents it from being added to this queue

peek

Added in API level 1

open fun peek(): E?

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
E?	the head of this queue, or null if this queue is empty

poll

Added in API level 1

open fun poll(): E?

Retrieves and removes the expired head of this queue, or returns null if this queue has no expired elements.

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

poll

Added in API level 1

open fun poll(
    timeout: Long, 
    unit: TimeUnit!
): E

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.

Parameters
timeout	Long: how long to wait before giving up, in units of unit
unit	TimeUnit!: a TimeUnit determining how to interpret the timeout parameter

Return
E	the expired head of this queue, or null if the specified waiting time elapses before an element with an expired delay becomes available

Exceptions
java.lang.InterruptedException	if interrupted while waiting

put

Added in API level 1

open fun put(e: E): Unit

Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

Parameters
e	E: the element to add

Exceptions
java.lang.InterruptedException	if interrupted while waiting
java.lang.ClassCastException	if the class of the specified element prevents it from being added to this queue
java.lang.NullPointerException	if the specified element is null
java.lang.IllegalArgumentException	if some property of the specified element prevents it from being added to this queue

remainingCapacity

Added in API level 1

open fun remainingCapacity(): Int

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

Return
Int	Integer.MAX_VALUE

remove

Added in API level 1

open fun remove(): E

Retrieves and removes the expired head of this queue, or throws an exception if this queue has no expired elements.

Return
E	the expired head of this queue

Exceptions
java.util.NoSuchElementException	if this queue has no elements with an expired delay

remove

Added in API level 1

open fun remove(element: E?): Boolean

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

Parameters
o	element to be removed from this queue, if present

Return
Boolean	true if this queue changed as a result of the call

Exceptions
java.lang.ClassCastException	if the class of the specified element is incompatible with this queue (optional)
java.lang.NullPointerException	if the specified element is null (optional)
java.lang.UnsupportedOperationException	if the remove operation is not supported by this collection

take

Added in API level 1

open fun take(): E

Retrieves and removes the expired head of this queue, waiting if necessary until an expired element is available on this queue.

Return
E	the expired head of this queue

Exceptions
java.lang.InterruptedException	if interrupted while waiting

toArray

Added in API level 1

open fun toArray(): Array<Any!>

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
Array<Any!>	an array containing all of the elements in this queue

toArray

Added in API level 1

open fun <T : Any!> toArray(a: Array<T>): Array<T>

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:

<code>Delayed[] a = q.toArray(new Delayed[0]);</code>

Note that toArray(new Object[0]) is identical in function to toArray().

Parameters
<T>	the component type of the array to contain the collection
a	Array<T>: 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
Array<T>	an array containing all of the elements in this queue

Exceptions
java.lang.ArrayStoreException	if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue
java.lang.NullPointerException	if the specified array is null

Properties

size

Added in API level 1

open val size: Int

Return
Int	the number of elements in this collection