Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Ctors](https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#pubctors) \| [Methods](https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#inhmethods)

# PriorityBlockingQueue


`
public


class
PriorityBlockingQueue
`


`


`

`


`

`

extends https://developer.android.com/reference/java/util/AbstractQueue<E>


`

`


implements

https://developer.android.com/reference/java/util/concurrent/BlockingQueue<E>,

https://developer.android.com/reference/java/io/Serializable


`

|---|---|---|---|
| [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.PriorityBlockingQueue\<E\> |

<br />

*** ** * ** ***

An unbounded [blocking queue](https://developer.android.com/reference/java/util/concurrent/BlockingQueue) that uses
the same ordering rules as class `https://developer.android.com/reference/java/util/PriorityQueue` and supplies
blocking retrieval operations. While this queue is logically
unbounded, attempted additions may fail due to resource exhaustion
(causing `OutOfMemoryError`). This class does not permit
`null` elements. A priority queue relying on [natural ordering](https://developer.android.com/reference/java/lang/Comparable) also does not permit insertion of
non-comparable objects (doing so results in
`ClassCastException`).

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.
The Iterator provided in method `https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#iterator()` and the
Spliterator provided in method `https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#spliterator()` are *not*
guaranteed to traverse the elements of the PriorityBlockingQueue in
any particular order. If you need ordered traversal, consider using
`Arrays.sort(pq.toArray())`. Also, method `drainTo` can
be used to *remove* some or all elements in priority order and
place them in another collection.

Operations on this class make no guarantees about the ordering
of elements with equal priority. If you need to enforce an
ordering, you can define custom classes or comparators that use a
secondary key to break ties in primary priority values. For
example, here is a class that applies first-in-first-out
tie-breaking to comparable elements. To use it, you would insert a
`new FIFOEntry(anEntry)` instead of a plain entry object.

    class FIFOEntry<E extends Comparable<? super E>>
        implements Comparable<FIFOEntry<E>> {
      static final AtomicLong seq = new AtomicLong();
      final long seqNum;
      final E entry;
      public FIFOEntry(E entry) {
        seqNum = seq.getAndIncrement();
        this.entry = entry;
      }
      public E getEntry() { return entry; }
      public int compareTo(FIFOEntry<E> other) {
        int res = entry.compareTo(other.entry);
        if (res == 0 && other.entry != this.entry)
          res = (seqNum < other.seqNum ? -1 : 1);
        return res;
      }
    }

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/PriorityBlockingQueue#PriorityBlockingQueue()() ` Creates a `PriorityBlockingQueue` with the default initial capacity (11) that orders its elements according to their [natural ordering](https://developer.android.com/reference/java/lang/Comparable). |
| ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#PriorityBlockingQueue(int)(int initialCapacity) ` Creates a `PriorityBlockingQueue` with the specified initial capacity that orders its elements according to their [natural ordering](https://developer.android.com/reference/java/lang/Comparable). |
| ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#PriorityBlockingQueue(int,%20java.util.Comparator<?%20super%20E>)(int initialCapacity, https://developer.android.com/reference/java/util/Comparator<? super E> comparator) ` Creates a `PriorityBlockingQueue` with the specified initial capacity that orders its elements according to the specified comparator. |
| ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#PriorityBlockingQueue(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Creates a `PriorityBlockingQueue` containing the elements in the specified collection. |

| ### Public methods ||
|---|---|
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#add(E)(E e) ` Inserts the specified element into this priority queue. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#clear()() ` Atomically removes all of the elements from this queue. |
| ` https://developer.android.com/reference/java/util/Comparator<? super E>` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#comparator()() ` Returns the comparator used to order the elements in this queue, or `null` if this queue uses the [natural ordering](https://developer.android.com/reference/java/lang/Comparable) of its elements. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#forEach(java.util.function.Consumer<?%20super%20E>)(https://developer.android.com/reference/java/util/function/Consumer<? super E> action) ` |
| ` https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#iterator()() ` Returns an iterator over the elements in this queue. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#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 priority queue. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#offer(E)(E e) ` Inserts the specified element into this priority queue. |
| ` E` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#put(E)(E e) ` Inserts the specified element into this priority queue. |
| ` int` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#remainingCapacity()() ` Always returns `Integer.MAX_VALUE` because a `PriorityBlockingQueue` is not capacity constrained. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#size()() ` Returns the number of elements in this collection. |
| ` https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#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/PriorityBlockingQueue#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/PriorityBlockingQueue#toArray()() ` Returns an array containing all of the elements in this queue. |
| ` <T> T[]` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#toArray(T[])(T[] a) ` Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array. |
| ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#toString()() ` Returns a string representation of this collection. |

| ### 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/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. | ||
| 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`. | ||

## Public constructors

### PriorityBlockingQueue

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public PriorityBlockingQueue ()
```

Creates a `PriorityBlockingQueue` with the default
initial capacity (11) that orders its elements according to
their [natural ordering](https://developer.android.com/reference/java/lang/Comparable).

<br />

### PriorityBlockingQueue

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public PriorityBlockingQueue (int initialCapacity)
```

Creates a `PriorityBlockingQueue` with the specified
initial capacity that orders its elements according to their
[natural ordering](https://developer.android.com/reference/java/lang/Comparable).

<br />

| Parameters ||
|---|---|
| `initialCapacity` | `int`: the initial capacity for this priority queue <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `initialCapacity` is less than 1 |

### PriorityBlockingQueue

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public PriorityBlockingQueue (int initialCapacity, 
                Comparator<? super E> comparator)
```

Creates a `PriorityBlockingQueue` with the specified initial
capacity that orders its elements according to the specified
comparator.

<br />

| Parameters ||
|---|---|
| `initialCapacity` | `int`: the initial capacity for this priority queue <br /> |
| `comparator` | `Comparator`: the comparator that will be used to order this priority queue. If `null`, the [natural ordering](https://developer.android.com/reference/java/lang/Comparable) of the elements will be used. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `initialCapacity` is less than 1 |

### PriorityBlockingQueue

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

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

Creates a `PriorityBlockingQueue` containing the elements
in the specified collection. If the specified collection is a
`https://developer.android.com/reference/java/util/SortedSet` or a `https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue`, this
priority queue will be ordered according to the same ordering.
Otherwise, this priority queue will be ordered according to the
[natural ordering](https://developer.android.com/reference/java/lang/Comparable) of its elements.

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: the collection whose elements are to be placed into this priority queue <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if elements of the specified collection cannot be compared to one another according to the priority queue's ordering |
| `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 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

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

Inserts the specified element into this priority queue.

<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/ClassCastException` | if the specified element cannot be compared with elements currently in the priority queue according to the priority queue's ordering |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### clear

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void clear ()
```

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

<br />

### comparator

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Comparator<? super E> comparator ()
```

Returns the comparator used to order the elements in this queue,
or `null` if this queue uses the [natural ordering](https://developer.android.com/reference/java/lang/Comparable) of its elements.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Comparator<? super E>` | the comparator used to order the elements in this queue, or `null` if this queue uses the natural ordering of its elements <br /> |

### contains

Added in [API level 1](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 1](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/ClassCastException` |   |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` |   |

### drainTo

Added in [API level 1](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/ClassCastException` |   |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` |   |

### 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` |   |

### iterator

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

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

Returns an iterator over the elements in this queue. The
iterator does not return the elements in any particular order.

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 <br /> |

### offer

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

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

Inserts the specified element into this priority 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`: This parameter is ignored as the method never blocks <br /> |
| `unit` | `TimeUnit`: This parameter is ignored as the method never blocks <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/ClassCastException` | if the specified element cannot be compared with elements currently in the priority queue according to the priority queue's ordering |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### offer

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

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

Inserts the specified element into this priority 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/ClassCastException` | if the specified element cannot be compared with elements currently in the priority queue according to the priority queue's ordering |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### peek

Added in [API level 1](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 1](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 1](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 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

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

Inserts the specified element into this priority 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/ClassCastException` | if the specified element cannot be compared with elements currently in the priority queue according to the priority queue's ordering |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null |

### remainingCapacity

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int remainingCapacity ()
```

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

<br />

| Returns ||
|---|---|
| `int` | `Integer.MAX_VALUE` always <br /> |

### remove

Added in [API level 1](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 and only 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 1](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 1](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 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public int size ()
```

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

<br />

| Returns ||
|---|---|
| `int` | the number of elements in this collection <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 spliterator does not traverse elements in any particular order
(the `https://developer.android.com/reference/java/util/Spliterator#ORDERED` characteristic is not reported).

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#SIZED` and
`https://developer.android.com/reference/java/util/Spliterator#NONNULL`.

<br />

##### Implementation Note:

- The `Spliterator` additionally reports `https://developer.android.com/reference/java/util/Spliterator#SUBSIZED`.

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

### take

Added in [API level 1](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 1](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.
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.

<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 1](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; 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 `https://developer.android.com/reference/java/util/concurrent/PriorityBlockingQueue#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 1](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 /> |