Added in API level 21

LinkedTransferQueue

open class LinkedTransferQueue<E : Any!> : AbstractQueue<E>, TransferQueue<E>, Serializable
kotlin.Any
   ↳ java.util.AbstractCollection<E>
   ↳ java.util.AbstractQueue<E>
   ↳ java.util.concurrent.LinkedTransferQueue

An unbounded TransferQueue based on linked nodes. This queue orders elements FIFO (first-in-first-out) with respect to any given producer. The head of the queue is that element that has been on the queue the longest time for some producer. The tail of the queue is that element that has been on the queue the shortest time for some producer.

Beware that, unlike in most collections, the size method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal.

Bulk operations that add, remove, or examine multiple elements, such as addAll, removeIf or forEach, are not guaranteed to be performed atomically. For example, a forEach traversal concurrent with an addAll operation might observe only some of the added elements.

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

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a LinkedTransferQueue happen-before actions subsequent to the access or removal of that element from the LinkedTransferQueue in another thread.

This class is a member of the Java Collections Framework.

Summary

Public constructors

Creates an initially empty LinkedTransferQueue.

Creates a LinkedTransferQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Public methods
open Boolean
add(element: E)

Inserts the specified element at the tail of this queue.

open Unit

open Boolean
contains(element: E?)

Returns true if this queue contains the specified element.

open Int

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

open Unit
forEach(action: Consumer<in E>)

open Int

open Boolean

open Boolean

Returns true if this queue contains no elements.

open MutableIterator<E>

Returns an iterator over the elements in this queue in proper sequence.

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

Inserts the specified element at the tail of this queue.

open Boolean
offer(e: E)

Inserts the specified element at the tail of this queue.

open E?

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

open E?

open Unit
put(e: E)

Inserts the specified element at the tail of this queue.

open Int

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

open Boolean
remove(element: E?)

Removes a single instance of the specified element from this queue, if it is present.

open Boolean
removeAll(elements: Collection<E>)

open Boolean
removeIf(filter: Predicate<in E>)

open Boolean
retainAll(elements: Collection<E>)

open Spliterator<E>

Returns a Spliterator over the elements in this queue.

open E

open Array<Any!>

Returns an array containing all of the elements in this queue, in proper sequence.

open Array<T>
toArray(a: Array<T>)

Returns an array containing all of the elements in this queue, in proper sequence; the runtime type of the returned array is that of the specified array.

open String

open Unit
transfer(e: E)

Transfers the element to a consumer, waiting if necessary to do so.

open Boolean

Transfers the element to a waiting consumer immediately, if possible.

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

Transfers the element to a consumer if it is possible to do so before the timeout elapses.

Inherited functions
Properties
open Int

Returns the number of elements in this queue.

Inherited properties

Public constructors

LinkedTransferQueue

Added in API level 21
LinkedTransferQueue()

Creates an initially empty LinkedTransferQueue.

LinkedTransferQueue

Added in API level 21
LinkedTransferQueue(c: MutableCollection<out E>!)

Creates a LinkedTransferQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator.

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 21
open fun add(element: E): Boolean

Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never throw IllegalStateException or return false.

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 21
open fun clear(): Unit
Exceptions
java.lang.UnsupportedOperationException if the clear operation is not supported by this collection

contains

Added in API level 21
open fun contains(element: E?): Boolean

Returns true if this queue contains the specified element. More formally, returns true if and only if this queue contains at least one element e such that o.equals(e).

Parameters
o object to be checked for containment in this queue
Return
Boolean true if this queue contains the specified element
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)

drainTo

Added in API level 21
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 21
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

forEach

Added in API level 24
open fun forEach(action: Consumer<in E>): Unit
Parameters
action Consumer<in E>: The action to be performed for each element
Exceptions
java.lang.NullPointerException if the specified action is null

getWaitingConsumerCount

Added in API level 21
open fun getWaitingConsumerCount(): Int
Return
Int the number of consumers waiting to receive elements

hasWaitingConsumer

Added in API level 21
open fun hasWaitingConsumer(): Boolean
Return
Boolean true if there is at least one waiting consumer

isEmpty

Added in API level 21
open fun isEmpty(): Boolean

Returns true if this queue contains no elements.

Return
Boolean true if this queue contains no elements

iterator

Added in API level 21
open fun iterator(): MutableIterator<E>

Returns an iterator over the elements in this queue in proper sequence. The elements will be returned in order from first (head) to last (tail).

The returned iterator is weakly consistent.

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

offer

Added in API level 21
open fun offer(
    e: E,
    timeout: Long,
    unit: TimeUnit!
): Boolean

Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never block or return false.

Parameters
e E: the element to add
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
Boolean true (as specified by BlockingQueue.offer)
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

offer

Added in API level 21
open fun offer(e: E): Boolean

Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never return false.

Parameters
e E: the element to add
Return
Boolean true (as specified by Queue#offer)
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

peek

Added in API level 21
open fun peek(): E?
Return
E? the head of this queue, or null if this queue is empty

poll

Added in API level 21
open fun poll(
    timeout: Long,
    unit: TimeUnit!
): E
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 head of this queue, or null if the specified waiting time elapses before an element is available
Exceptions
java.lang.InterruptedException if interrupted while waiting

poll

Added in API level 21
open fun poll(): E?
Return
E? the head of this queue, or null if this queue is empty

put

Added in API level 21
open fun put(e: E): Unit

Inserts the specified element at the tail of this 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 21
open fun remainingCapacity(): Int

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

Return
Int Integer.MAX_VALUE (as specified by BlockingQueue#remainingCapacity())

remove

Added in API level 21
open fun remove(element: E?): Boolean

Removes a single instance of the specified element from this queue, if it is present. More formally, removes an element e such that o.equals(e), if this queue contains one or more such elements. Returns true if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).

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

removeAll

Added in API level 21
open fun removeAll(elements: Collection<E>): Boolean
Parameters
c collection containing elements to be removed from this collection
Return
Boolean true if this collection changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the removeAll method is not supported by this collection
java.lang.ClassCastException if the types of one or more elements in this collection are incompatible with the specified collection (optional)
java.lang.NullPointerException if this collection contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null

removeIf

Added in API level 24
open fun removeIf(filter: Predicate<in E>): Boolean
Parameters
filter Predicate<in E>: a predicate which returns true for elements to be removed
Return
Boolean true if any elements were removed
Exceptions
java.lang.NullPointerException if the specified filter is null
java.lang.UnsupportedOperationException if elements cannot be removed from this collection. Implementations may throw this exception if a matching element cannot be removed or if, in general, removal is not supported.

retainAll

Added in API level 21
open fun retainAll(elements: Collection<E>): Boolean
Parameters
c collection containing elements to be retained in this collection
Return
Boolean true if this collection changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the retainAll operation is not supported by this collection
java.lang.ClassCastException if the types of one or more elements in this collection are incompatible with the specified collection (optional)
java.lang.NullPointerException if this collection contains one or more null elements and the specified collection does not permit null elements (optional), or if the specified collection is null

spliterator

Added in API level 24
open fun spliterator(): Spliterator<E>

Returns a Spliterator over the elements in this queue.

The returned spliterator is weakly consistent.

The Spliterator reports Spliterator#CONCURRENT, Spliterator#ORDERED, and Spliterator#NONNULL.

Return
Spliterator<E> a Spliterator over the elements in this queue

take

Added in API level 21
open fun take(): E
Return
E the head of this queue
Exceptions
java.lang.InterruptedException if interrupted while waiting

toArray

Added in API level 21
open fun toArray(): Array<Any!>

Returns an array containing all of the elements in this queue, in proper sequence.

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 21
open fun <T : Any!> toArray(a: Array<T>): Array<T>

Returns an array containing all of the elements in this queue, in proper sequence; the runtime type of the returned array is that of the specified array. 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.

Suppose x is a queue known to contain only strings. The following code can be used to dump the queue into a newly allocated array of String:

<code>String[] y = x.toArray(new String[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

toString

Added in API level 21
open fun toString(): String
Return
String a string representation of the object.

transfer

Added in API level 21
open fun transfer(e: E): Unit

Transfers the element to a consumer, waiting if necessary to do so.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take or timed poll), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer.

Parameters
e E: the element to transfer
Exceptions
java.lang.InterruptedException if interrupted while waiting, in which case the element is not left enqueued
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

tryTransfer

Added in API level 21
open fun tryTransfer(e: E): Boolean

Transfers the element to a waiting consumer immediately, if possible.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take or timed poll), otherwise returning false without enqueuing the element.

Parameters
e E: the element to transfer
Return
Boolean true if the element was transferred, else false
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

tryTransfer

Added in API level 21
open fun tryTransfer(
    e: E,
    timeout: Long,
    unit: TimeUnit!
): Boolean

Transfers the element to a consumer if it is possible to do so before the timeout elapses.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take or timed poll), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer, returning false if the specified wait time elapses before the element can be transferred.

Parameters
e E: the element to transfer
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
Boolean true if successful, or false if the specified waiting time elapses before completion, in which case the element is not left enqueued
Exceptions
java.lang.InterruptedException if interrupted while waiting, in which case the element is not left enqueued
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

Properties

size

Added in API level 21
open val size: Int

Returns the number of elements in this queue. If this queue contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires an O(n) traversal.

Return
Int the number of elements in this queue