Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Ctors](https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#pubctors) \| [Methods](https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#inhmethods)

# LinkedTransferQueue

` public class LinkedTransferQueue `   
` ` ` ` ` extends https://developer.android.com/reference/java/util/AbstractQueue<E> ` ` implements https://developer.android.com/reference/java/io/Serializable, https://developer.android.com/reference/java/util/concurrent/TransferQueue<E> `

|---|---|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||||
| ↳ | [java.util.AbstractCollection](https://developer.android.com/reference/java/util/AbstractCollection)\<E\> |||
|   | ↳ | [java.util.AbstractQueue](https://developer.android.com/reference/java/util/AbstractQueue)\<E\> ||
|   |   | ↳ | java.util.concurrent.LinkedTransferQueue\<E\> |

<br />

*** ** * ** ***

An unbounded `https://developer.android.com/reference/java/util/concurrent/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 `https://developer.android.com/reference/java/util/AbstractQueue#addAll(java.util.Collection<?%20extends%20E>)`, `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#removeIf(java.util.function.Predicate<?%20super%20E>)` or `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#forEach(java.util.function.Consumer<?%20super%20E>)`, 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 `https://developer.android.com/reference/java/util/Collection` and `https://developer.android.com/reference/java/util/Iterator` interfaces.

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a `LinkedTransferQueue` [*happen-before*](https://developer.android.com/reference/java/util/concurrent/package-summary#MemoryVisibility) 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](https://reference/java/util/package-summary.html#CollectionsFramework).

## Summary

| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#LinkedTransferQueue()() ` Creates an initially empty `LinkedTransferQueue`. |
| ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#LinkedTransferQueue(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Creates a `LinkedTransferQueue` initially containing the elements of the given collection, added in traversal order of the collection's iterator. |

| ### Public methods ||
|---|---|
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#add(E)(E e) ` Inserts the specified element at the tail of this queue. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#clear()() ` Removes all of the elements from this queue. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this queue contains the specified element. |
| ` int` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#drainTo(java.util.Collection<?%20super%20E>,%20int)(https://developer.android.com/reference/java/util/Collection<? super E> c, int maxElements) ` Removes at most the given number of available elements from this queue and adds them to the given collection. |
| ` int` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#drainTo(java.util.Collection<?%20super%20E>)(https://developer.android.com/reference/java/util/Collection<? super E> c) ` Removes all available elements from this queue and adds them to the given collection. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#forEach(java.util.function.Consumer<?%20super%20E>)(https://developer.android.com/reference/java/util/function/Consumer<? super E> action) ` |
| ` int` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#getWaitingConsumerCount()() ` Returns an estimate of the number of consumers waiting to receive elements via `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)`. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#hasWaitingConsumer()() ` Returns `true` if there is at least one consumer waiting to receive an element via `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)`. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#isEmpty()() ` Returns `true` if this queue contains no elements. |
| ` https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#iterator()() ` Returns an iterator over the elements in this queue in proper sequence. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#offer(E,%20long,%20java.util.concurrent.TimeUnit)(E e, long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) ` Inserts the specified element at the tail of this queue. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#offer(E)(E e) ` Inserts the specified element at the tail of this queue. |
| ` E` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#peek()() ` Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty. |
| ` E` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#poll(long,%20java.util.concurrent.TimeUnit)(long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) ` Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available. |
| ` E` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#poll()() ` Retrieves and removes the head of this queue, or returns `null` if this queue is empty. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#put(E)(E e) ` Inserts the specified element at the tail of this queue. |
| ` int` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#remainingCapacity()() ` Always returns `Integer.MAX_VALUE` because a `LinkedTransferQueue` is not capacity constrained. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes a single instance of the specified element from this queue, if it is present. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes all of this collection's elements that are also contained in the specified collection (optional operation). |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#removeIf(java.util.function.Predicate<?%20super%20E>)(https://developer.android.com/reference/java/util/function/Predicate<? super E> filter) ` Removes all of the elements of this collection that satisfy the given predicate (optional operation). |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Retains only the elements in this collection that are contained in the specified collection (optional operation). |
| ` int` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#size()() ` Returns the number of elements in this queue. |
| ` https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#spliterator()() ` Returns a `https://developer.android.com/reference/java/util/Spliterator` over the elements in this queue. |
| ` E` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#take()() ` Retrieves and removes the head of this queue, waiting if necessary until an element becomes available. |
| ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#toArray()() ` Returns an array containing all of the elements in this queue, in proper sequence. |
| ` <T> T[]` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#toArray(T[])(T[] a) ` 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. |
| ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#toString()() ` Returns a string representation of this collection. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#transfer(E)(E e) ` Transfers the element to a consumer, waiting if necessary to do so. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#tryTransfer(E)(E e) ` Transfers the element to a waiting consumer immediately, if possible. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#tryTransfer(E,%20long,%20java.util.concurrent.TimeUnit)(E e, long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) ` Transfers the element to a consumer if it is possible to do so before the timeout elapses. |

### Inherited methods

From class ` https://developer.android.com/reference/java/util/AbstractQueue ` ` boolean` ` https://developer.android.com/reference/java/util/AbstractQueue#add(E)(E e) `

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and throwing an `IllegalStateException` if no space is currently available.
` boolean` ` https://developer.android.com/reference/java/util/AbstractQueue#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) `

Adds all of the elements in the specified collection to this queue.
` void` ` https://developer.android.com/reference/java/util/AbstractQueue#clear()() `

Removes all of the elements from this queue.
` E` ` https://developer.android.com/reference/java/util/AbstractQueue#element()() `

Retrieves, but does not remove, the head of this queue.
` E` ` https://developer.android.com/reference/java/util/AbstractQueue#remove()() `

Retrieves and removes the head of this queue.
From class ` https://developer.android.com/reference/java/util/AbstractCollection ` ` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#add(E)(E e) `

Ensures that this collection contains the specified element (optional operation).
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) `

Adds all of the elements in the specified collection to this collection (optional operation).
` void` ` https://developer.android.com/reference/java/util/AbstractCollection#clear()() `

Removes all of the elements from this collection (optional operation).
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Returns `true` if this collection contains the specified element.
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) `

Returns `true` if this collection contains all of the elements in the specified collection.
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#isEmpty()() `

Returns `true` if this collection contains no elements.
` abstract https://developer.android.com/reference/java/util/Iterator<E>` ` https://developer.android.com/reference/java/util/AbstractCollection#iterator()() `

Returns an iterator over the elements contained in this collection.
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Removes a single instance of the specified element from this collection, if it is present (optional operation).
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) `

Removes all of this collection's elements that are also contained in the specified collection (optional operation).
` boolean` ` https://developer.android.com/reference/java/util/AbstractCollection#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) `

Retains only the elements in this collection that are contained in the specified collection (optional operation).
` abstract int` ` https://developer.android.com/reference/java/util/AbstractCollection#size()() `

Returns the number of elements in this collection.
` <T> T[]` ` https://developer.android.com/reference/java/util/AbstractCollection#toArray(T[])(T[] a) `

Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
` https://developer.android.com/reference/java/lang/Object` ` https://developer.android.com/reference/java/util/AbstractCollection#toArray()() `

Returns an array containing all of the elements in this collection.
` https://developer.android.com/reference/java/lang/String` ` https://developer.android.com/reference/java/util/AbstractCollection#toString()() `

Returns a string representation of this collection.
From class ` https://developer.android.com/reference/java/lang/Object ` ` https://developer.android.com/reference/java/lang/Object` ` https://developer.android.com/reference/java/lang/Object#clone()() `

Creates and returns a copy of this object.
` boolean` ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) `

Indicates whether some other object is "equal to" this one.
` void` ` https://developer.android.com/reference/java/lang/Object#finalize()() `

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
` final https://developer.android.com/reference/java/lang/Class<?>` ` https://developer.android.com/reference/java/lang/Object#getClass()() `

Returns the runtime class of this `Object`.
` int` ` https://developer.android.com/reference/java/lang/Object#hashCode()() `

Returns a hash code value for the object.
` final void` ` https://developer.android.com/reference/java/lang/Object#notify()() `

Wakes up a single thread that is waiting on this object's monitor.
` final void` ` https://developer.android.com/reference/java/lang/Object#notifyAll()() `

Wakes up all threads that are waiting on this object's monitor.
` https://developer.android.com/reference/java/lang/String` ` https://developer.android.com/reference/java/lang/Object#toString()() `

Returns a string representation of the object.
` final void` ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) `

Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed.
` final void` ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) `

Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed.
` final void` ` https://developer.android.com/reference/java/lang/Object#wait()() `

Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*.
From interface ` https://developer.android.com/reference/java/util/Queue ` ` abstract boolean` ` https://developer.android.com/reference/java/util/Queue#add(E)(E e) `

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and throwing an `IllegalStateException` if no space is currently available.
` abstract E` ` https://developer.android.com/reference/java/util/Queue#element()() `

Retrieves, but does not remove, the head of this queue.
` abstract boolean` ` https://developer.android.com/reference/java/util/Queue#offer(E)(E e) `

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions.
` abstract E` ` https://developer.android.com/reference/java/util/Queue#peek()() `

Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty.
` abstract E` ` https://developer.android.com/reference/java/util/Queue#poll()() `

Retrieves and removes the head of this queue, or returns `null` if this queue is empty.
` abstract E` ` https://developer.android.com/reference/java/util/Queue#remove()() `

Retrieves and removes the head of this queue.
From interface ` https://developer.android.com/reference/java/util/Collection ` ` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#add(E)(E e) `

Ensures that this collection contains the specified element (optional operation).
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) `

Adds all of the elements in the specified collection to this collection (optional operation).
` abstract void` ` https://developer.android.com/reference/java/util/Collection#clear()() `

Removes all of the elements from this collection (optional operation).
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Returns `true` if this collection contains the specified element.
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) `

Returns `true` if this collection contains all of the elements in the specified collection.
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Compares the specified object with this collection for equality.
` abstract int` ` https://developer.android.com/reference/java/util/Collection#hashCode()() `

Returns the hash code value for this collection.
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#isEmpty()() `

Returns `true` if this collection contains no elements.
` abstract https://developer.android.com/reference/java/util/Iterator<E>` ` https://developer.android.com/reference/java/util/Collection#iterator()() `

Returns an iterator over the elements in this collection.
` default https://developer.android.com/reference/java/util/stream/Stream<E>` ` https://developer.android.com/reference/java/util/Collection#parallelStream()() `

Returns a possibly parallel `Stream` with this collection as its source.
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Removes a single instance of the specified element from this collection, if it is present (optional operation).
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) `

Removes all of this collection's elements that are also contained in the specified collection (optional operation).
` default boolean` ` https://developer.android.com/reference/java/util/Collection#removeIf(java.util.function.Predicate<?%20super%20E>)(https://developer.android.com/reference/java/util/function/Predicate<? super E> filter) `

Removes all of the elements of this collection that satisfy the given predicate (optional operation).
` abstract boolean` ` https://developer.android.com/reference/java/util/Collection#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) `

Retains only the elements in this collection that are contained in the specified collection (optional operation).
` abstract int` ` https://developer.android.com/reference/java/util/Collection#size()() `

Returns the number of elements in this collection.
` default https://developer.android.com/reference/java/util/Spliterator<E>` ` https://developer.android.com/reference/java/util/Collection#spliterator()() `

Creates a `https://developer.android.com/reference/java/util/Spliterator` over the elements in this collection.
` default https://developer.android.com/reference/java/util/stream/Stream<E>` ` https://developer.android.com/reference/java/util/Collection#stream()() `

Returns a sequential `Stream` with this collection as its source.
` abstract <T> T[]` ` https://developer.android.com/reference/java/util/Collection#toArray(T[])(T[] a) `

Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
` abstract https://developer.android.com/reference/java/lang/Object` ` https://developer.android.com/reference/java/util/Collection#toArray()() `

Returns an array containing all of the elements in this collection.
` default <T> T[]` ` https://developer.android.com/reference/java/util/Collection#toArray(java.util.function.IntFunction<T[]>)(https://developer.android.com/reference/java/util/function/IntFunction<T[]> generator) `

Returns an array containing all of the elements in this collection, using the provided `generator` function to allocate the returned array.
From interface ` https://developer.android.com/reference/java/util/concurrent/TransferQueue ` ` abstract int` ` https://developer.android.com/reference/java/util/concurrent/TransferQueue#getWaitingConsumerCount()() `

Returns an estimate of the number of consumers waiting to receive elements via `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)`.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/TransferQueue#hasWaitingConsumer()() `

Returns `true` if there is at least one consumer waiting to receive an element via `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)`.
` abstract void` ` https://developer.android.com/reference/java/util/concurrent/TransferQueue#transfer(E)(E e) `

Transfers the element to a consumer, waiting if necessary to do so.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/TransferQueue#tryTransfer(E)(E e) `

Transfers the element to a waiting consumer immediately, if possible.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/TransferQueue#tryTransfer(E,%20long,%20java.util.concurrent.TimeUnit)(E e, long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) `

Transfers the element to a consumer if it is possible to do so before the timeout elapses.
From interface ` https://developer.android.com/reference/java/lang/Iterable ` ` default void` ` https://developer.android.com/reference/java/lang/Iterable#forEach(java.util.function.Consumer<?%20super%20T>)(https://developer.android.com/reference/java/util/function/Consumer<? super T> action) `

Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception.
` abstract https://developer.android.com/reference/java/util/Iterator<E>` ` https://developer.android.com/reference/java/lang/Iterable#iterator()() `

Returns an iterator over elements of type `T`.
` default https://developer.android.com/reference/java/util/Spliterator<E>` ` https://developer.android.com/reference/java/lang/Iterable#spliterator()() `

Creates a `https://developer.android.com/reference/java/util/Spliterator` over the elements described by this `Iterable`.
From interface ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue ` ` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#add(E)(E e) `

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and throwing an `IllegalStateException` if no space is currently available.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Returns `true` if this queue contains the specified element.
` abstract int` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#drainTo(java.util.Collection<?%20super%20E>)(https://developer.android.com/reference/java/util/Collection<? super E> c) `

Removes all available elements from this queue and adds them to the given collection.
` abstract int` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#drainTo(java.util.Collection<?%20super%20E>,%20int)(https://developer.android.com/reference/java/util/Collection<? super E> c, int maxElements) `

Removes at most the given number of available elements from this queue and adds them to the given collection.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#offer(E)(E e) `

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and `false` if no space is currently available.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#offer(E,%20long,%20java.util.concurrent.TimeUnit)(E e, long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) `

Inserts the specified element into this queue, waiting up to the specified wait time if necessary for space to become available.
` abstract E` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)(long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) `

Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
` abstract void` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#put(E)(E e) `

Inserts the specified element into this queue, waiting if necessary for space to become available.
` abstract int` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#remainingCapacity()() `

Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking, or `Integer.MAX_VALUE` if there is no intrinsic limit.
` abstract boolean` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) `

Removes a single instance of the specified element from this queue, if it is present.
` abstract E` ` https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()() `

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

## Public constructors

### LinkedTransferQueue

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public LinkedTransferQueue ()
```

Creates an initially empty `LinkedTransferQueue`.

<br />

### LinkedTransferQueue

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public LinkedTransferQueue (Collection<? extends E> c)
```

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

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: the collection of elements to initially contain <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified collection or any of its elements are null |

## Public methods

### add

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean add (E e)
```

Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never throw `https://developer.android.com/reference/java/lang/IllegalStateException` or return `false`.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to add <br /> |

| Returns ||
|---|---|
| `boolean` | `true` (as specified by `https://developer.android.com/reference/java/util/Collection#add(E)`) <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### clear

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void clear ()
```

Removes all of the elements from this queue. The queue will be empty after this call returns.

This implementation repeatedly invokes `https://developer.android.com/reference/java/util/Queue#poll()` until it returns `null`.

<br />

### contains

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean contains (Object o)
```

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)`.

<br />

| Parameters ||
|---|---|
| `o` | `Object`: object to be checked for containment in this queue <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if this queue contains the specified element <br /> |

### drainTo

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int drainTo (Collection<? super E> c, 
                int maxElements)
```

Removes at most the given number of available elements from this queue and adds them to the given collection. A failure encountered while attempting to add elements to collection `c` 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.

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: the collection to transfer elements into <br /> |
| `maxElements` | `int`: the maximum number of elements to transfer <br /> |

| Returns ||
|---|---|
| `int` | the number of elements transferred <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### drainTo

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int drainTo (Collection<? super E> c)
```

Removes all available elements from this queue and adds them to the given collection. This operation may be more efficient than repeatedly polling this queue. A failure encountered while attempting to add elements to collection `c` 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.

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: the collection to transfer elements into <br /> |

| Returns ||
|---|---|
| `int` | the number of elements transferred <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### forEach

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void forEach (Consumer<? super E> action)
```

<br />

<br />

| Parameters ||
|---|---|
| `action` | `Consumer` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### getWaitingConsumerCount

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int getWaitingConsumerCount ()
```

Returns an estimate of the number of consumers waiting to receive elements via `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)`. The return value is an approximation of a momentary state of affairs, that may be inaccurate if consumers have completed or given up waiting. The value may be useful for monitoring and heuristics, but not for synchronization control. Implementations of this method are likely to be noticeably slower than those for `https://developer.android.com/reference/java/util/concurrent/TransferQueue#hasWaitingConsumer()`.

<br />

| Returns ||
|---|---|
| `int` | the number of consumers waiting to receive elements <br /> |

### hasWaitingConsumer

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean hasWaitingConsumer ()
```

Returns `true` if there is at least one consumer waiting to receive an element via `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#poll(long,%20java.util.concurrent.TimeUnit)`. The return value represents a momentary state of affairs.

<br />

| Returns ||
|---|---|
| `boolean` | `true` if there is at least one waiting consumer <br /> |

### isEmpty

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean isEmpty ()
```

Returns `true` if this queue contains no elements.

<br />

| Returns ||
|---|---|
| `boolean` | `true` if this queue contains no elements <br /> |

### iterator

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Iterator<E> iterator ()
```

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*](https://developer.android.com/reference/java/util/concurrent/package-summary#Weakly).

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Iterator<E>` | an iterator over the elements in this queue in proper sequence <br /> |

### offer

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean offer (E e, 
                long timeout, 
                TimeUnit unit)
```

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

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to add <br /> |
| `timeout` | `long`: how long to wait before giving up, in units of `unit` <br /> |
| `unit` | `TimeUnit`: a `TimeUnit` determining how to interpret the `timeout` parameter <br /> |

| Returns ||
|---|---|
| `boolean` | `true` (as specified by `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#offer(E,%20long,%20java.util.concurrent.TimeUnit)`) <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### offer

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean offer (E e)
```

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

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to add <br /> |

| Returns ||
|---|---|
| `boolean` | `true` (as specified by `https://developer.android.com/reference/java/util/Queue#offer(E)`) <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### peek

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E peek ()
```

Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty.

<br />

| Returns ||
|---|---|
| `E` | the head of this queue, or `null` if this queue is empty <br /> |

### poll

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E poll (long timeout, 
                TimeUnit unit)
```

Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.

<br />

| Parameters ||
|---|---|
| `timeout` | `long`: how long to wait before giving up, in units of `unit` <br /> |
| `unit` | `TimeUnit`: a `TimeUnit` determining how to interpret the `timeout` parameter <br /> |

| Returns ||
|---|---|
| `E` | the head of this queue, or `null` if the specified waiting time elapses before an element is available <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/InterruptedException` |   |

### poll

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E poll ()
```

Retrieves and removes the head of this queue, or returns `null` if this queue is empty.

<br />

| Returns ||
|---|---|
| `E` | the head of this queue, or `null` if this queue is empty <br /> |

### put

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void put (E e)
```

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

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to add <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### remainingCapacity

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int remainingCapacity ()
```

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

<br />

| Returns ||
|---|---|
| `int` | `Integer.MAX_VALUE` (as specified by `https://developer.android.com/reference/java/util/concurrent/BlockingQueue#remainingCapacity()`) <br /> |

### remove

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean remove (Object o)
```

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).

<br />

| Parameters ||
|---|---|
| `o` | `Object`: element to be removed from this queue, if present <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if this queue changed as a result of the call <br /> |

### removeAll

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean removeAll (Collection<?> c)
```

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.

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: collection containing elements to be removed from this collection <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if this collection changed as a result of the call <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### removeIf

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean removeIf (Predicate<? super E> filter)
```

Removes all of the elements of this collection that satisfy the given predicate (optional operation). Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller.

<br />

| Parameters ||
|---|---|
| `filter` | `Predicate`: a predicate which returns `true` for elements to be removed <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if any elements were removed <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### retainAll

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean retainAll (Collection<?> c)
```

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.

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: collection containing elements to be retained in this collection <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if this collection changed as a result of the call <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### size

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int size ()
```

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.

<br />

| Returns ||
|---|---|
| `int` | the number of elements in this queue <br /> |

### spliterator

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Spliterator<E> spliterator ()
```

Returns a `https://developer.android.com/reference/java/util/Spliterator` over the elements in this queue.

The returned spliterator is [*weakly consistent*](https://developer.android.com/reference/java/util/concurrent/package-summary#Weakly).

The `Spliterator` reports `https://developer.android.com/reference/java/util/Spliterator#CONCURRENT`, `https://developer.android.com/reference/java/util/Spliterator#ORDERED`, and `https://developer.android.com/reference/java/util/Spliterator#NONNULL`.

<br />

##### Implementation Note:

- The `Spliterator` implements `trySplit` to permit limited parallelism.

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Spliterator<E>` | a `Spliterator` over the elements in this queue <br /> |

### take

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E take ()
```

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

<br />

| Returns ||
|---|---|
| `E` | the head of this queue <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/InterruptedException` |   |

### toArray

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Object[] toArray ()
```

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.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/Object` | an array containing all of the elements in this queue <br /> |

### toArray

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public T[] toArray (T[] a)
```

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 `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#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`:

     String[] y = x.toArray(new String[0]);

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

<br />

<br />

| Parameters ||
|---|---|
| `a` | `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 <br /> |

| Returns ||
|---|---|
| `T[]` | an array containing all of the elements in this queue <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/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 |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified array is null |

### toString

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public 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 `https://developer.android.com/reference/java/lang/String#valueOf(java.lang.Object)`.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | a string representation of this collection <br /> |

### transfer

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void transfer (E e)
```

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 `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#poll(long,%20java.util.concurrent.TimeUnit)`), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to transfer <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |
| `https://developer.android.com/reference/java/lang/InterruptedException` |   |

### tryTransfer

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean tryTransfer (E e)
```

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 `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#poll(long,%20java.util.concurrent.TimeUnit)`), otherwise returning `false` without enqueuing the element.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to transfer <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if the element was transferred, else `false` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### tryTransfer

Added in [API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean tryTransfer (E e, 
                long timeout, 
                TimeUnit unit)
```

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 `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#take()` or timed `https://developer.android.com/reference/java/util/concurrent/LinkedTransferQueue#poll(long,%20java.util.concurrent.TimeUnit)`), 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.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to transfer <br /> |
| `timeout` | `long`: how long to wait before giving up, in units of `unit` <br /> |
| `unit` | `TimeUnit`: a `TimeUnit` determining how to interpret the `timeout` parameter <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if successful, or `false` if the specified waiting time elapses before completion, in which case the element is not left enqueued <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |
| `https://developer.android.com/reference/java/lang/InterruptedException` |   |