Added in API level 9

Summary: Ctors | Methods | Inherited Methods

LinkedBlockingDeque

public class LinkedBlockingDeque
extends AbstractQueue<E> implements BlockingDeque<E>, Serializable

java.lang.Object
↳	java.util.AbstractCollection<E>
	↳	java.util.AbstractQueue<E>
		↳	java.util.concurrent.LinkedBlockingDeque<E>

An optionally-bounded blocking deque based on linked nodes.

The optional capacity bound constructor argument serves as a way to prevent excessive expansion. The capacity, if unspecified, is equal to Integer.MAX_VALUE. Linked nodes are dynamically created upon each insertion unless this would bring the deque above capacity.

Most operations run in constant time (ignoring time spent blocking). Exceptions include remove, removeFirstOccurrence, removeLastOccurrence, contains, iterator.remove(), and the bulk operations, all of which run in linear time.

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

This class is a member of the Java Collections Framework.

Summary

Public constructors
`LinkedBlockingDeque()` Creates a `LinkedBlockingDeque` with a capacity of `Integer.MAX_VALUE`.
`LinkedBlockingDeque(int capacity)` Creates a `LinkedBlockingDeque` with the given (fixed) capacity.
`LinkedBlockingDeque(Collection<? extends E> c)` Creates a `LinkedBlockingDeque` with a capacity of `Integer.MAX_VALUE`, initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Public methods
`boolean`	`add(E e)` Inserts the specified element at the end of this deque unless it would violate capacity restrictions.
`boolean`	`addAll(Collection<? extends E> c)` Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator.
`void`	`addFirst(E e)` Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`void`	`addLast(E e)` Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`void`	`clear()` Atomically removes all of the elements from this deque.
`boolean`	`contains(Object o)` Returns `true` if this deque contains the specified element.
`Iterator<E>`	`descendingIterator()` Returns an iterator over the elements in this deque in reverse sequential order.
`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.
`int`	`drainTo(Collection<? super E> c)` Removes all available elements from this queue and adds them to the given collection.
`E`	`element()` Retrieves, but does not remove, the head of the queue represented by this deque.
`void`	`forEach(Consumer<? super E> action)`
`E`	`getFirst()` Retrieves, but does not remove, the first element of this deque.
`E`	`getLast()` Retrieves, but does not remove, the last element of this deque.
`Iterator<E>`	`iterator()` Returns an iterator over the elements in this deque in proper sequence.
`boolean`	`offer(E e, long timeout, TimeUnit unit)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available.
`boolean`	`offer(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and `false` if no space is currently available.
`boolean`	`offerFirst(E e)` Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and `false` if no space is currently available.
`boolean`	`offerFirst(E e, long timeout, TimeUnit unit)` Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.
`boolean`	`offerLast(E e)` Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and `false` if no space is currently available.
`boolean`	`offerLast(E e, long timeout, TimeUnit unit)` Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.
`E`	`peek()` Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty.
`E`	`peekFirst()` Retrieves, but does not remove, the first element of this deque, or returns `null` if this deque is empty.
`E`	`peekLast()` Retrieves, but does not remove, the last element of this deque, or returns `null` if this deque is empty.
`E`	`poll(long timeout, TimeUnit unit)` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available.
`E`	`poll()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty.
`E`	`pollFirst()` Retrieves and removes the first element of this deque, or returns `null` if this deque is empty.
`E`	`pollFirst(long timeout, TimeUnit unit)` Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.
`E`	`pollLast()` Retrieves and removes the last element of this deque, or returns `null` if this deque is empty.
`E`	`pollLast(long timeout, TimeUnit unit)` Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.
`E`	`pop()` Pops an element from the stack represented by this deque.
`void`	`push(E e)` Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`void`	`put(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.
`void`	`putFirst(E e)` Inserts the specified element at the front of this deque, waiting if necessary for space to become available.
`void`	`putLast(E e)` Inserts the specified element at the end of this deque, waiting if necessary for space to become available.
`int`	`remainingCapacity()` Returns the number of additional elements that this deque can ideally (in the absence of memory or resource constraints) accept without blocking.
`boolean`	`remove(Object o)` Removes the first occurrence of the specified element from this deque.
`E`	`remove()` Retrieves and removes the head of the queue represented by this deque.
`boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`E`	`removeFirst()` Retrieves and removes the first element of this deque.
`boolean`	`removeFirstOccurrence(Object o)` Removes the first occurrence of the specified element from this deque.
`boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`E`	`removeLast()` Retrieves and removes the last element of this deque.
`boolean`	`removeLastOccurrence(Object o)` Removes the last occurrence of the specified element from this deque.
`boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`int`	`size()` Returns the number of elements in this deque.
`Spliterator<E>`	`spliterator()` Returns a `Spliterator` over the elements in this deque.
`E`	`take()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available.
`E`	`takeFirst()` Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.
`E`	`takeLast()` Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.
`Object[]`	`toArray()` Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).
`<T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this deque, in proper sequence; the runtime type of the returned array is that of the specified array.
`String`	`toString()` Returns a string representation of this collection.

Inherited methods

From class


        
          java.util.AbstractQueue

`boolean`	`add(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`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this queue.
`void`	`clear()` Removes all of the elements from this queue.
`E`	`element()` Retrieves, but does not remove, the head of this queue.
`E`	`remove()` Retrieves and removes the head of this queue.

From class


        
          java.util.AbstractCollection

`boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`void`	`clear()` Removes all of the elements from this collection (optional operation).
`boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements contained in this collection.
`boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`abstract int`	`size()` Returns the number of elements in this collection.
`<T> T[]`	`toArray(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.
`Object[]`	`toArray()` Returns an array containing all of the elements in this collection.
`String`	`toString()` Returns a string representation of this collection.

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(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`	`wait(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`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.util.Queue

`abstract boolean`	`add(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`	`element()` Retrieves, but does not remove, the head of this queue.
`abstract boolean`	`offer(E e)` Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions.
`abstract E`	`peek()` Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty.
`abstract E`	`poll()` Retrieves and removes the head of this queue, or returns `null` if this queue is empty.
`abstract E`	`remove()` Retrieves and removes the head of this queue.

From interface


        
          java.util.Collection

`abstract boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`abstract boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`abstract void`	`clear()` Removes all of the elements from this collection (optional operation).
`abstract boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`abstract boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`abstract boolean`	`equals(Object o)` Compares the specified object with this collection for equality.
`abstract int`	`hashCode()` Returns the hash code value for this collection.
`abstract boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this collection.
`default Stream<E>`	`parallelStream()` Returns a possibly parallel `Stream` with this collection as its source.
`abstract boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`abstract boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`default boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`abstract boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`abstract int`	`size()` Returns the number of elements in this collection.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this collection.
`default Stream<E>`	`stream()` Returns a sequential `Stream` with this collection as its source.
`abstract <T> T[]`	`toArray(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 Object[]`	`toArray()` Returns an array containing all of the elements in this collection.
`default <T> T[]`	`toArray(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


        
          java.util.concurrent.BlockingDeque

`abstract boolean`	`add(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) 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 void`	`addFirst(E e)` Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`abstract void`	`addLast(E e)` Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`abstract boolean`	`contains(Object o)` Returns `true` if this deque contains the specified element.
`abstract E`	`element()` Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque).
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this deque in proper sequence.
`abstract boolean`	`offer(E e, long timeout, TimeUnit unit)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available.
`abstract boolean`	`offer(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) 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`	`offerFirst(E e)` Inserts the specified element at the front of this deque 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`	`offerFirst(E e, long timeout, TimeUnit unit)` Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.
`abstract boolean`	`offerLast(E e)` Inserts the specified element at the end of this deque 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`	`offerLast(E e, long timeout, TimeUnit unit)` Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.
`abstract E`	`peek()` Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty.
`abstract E`	`poll(long timeout, TimeUnit unit)` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available.
`abstract E`	`poll()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty.
`abstract E`	`pollFirst(long timeout, TimeUnit unit)` Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.
`abstract E`	`pollLast(long timeout, TimeUnit unit)` Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.
`abstract void`	`push(E e)` Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`abstract void`	`put(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.
`abstract void`	`putFirst(E e)` Inserts the specified element at the front of this deque, waiting if necessary for space to become available.
`abstract void`	`putLast(E e)` Inserts the specified element at the end of this deque, waiting if necessary for space to become available.
`abstract E`	`remove()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque).
`abstract boolean`	`remove(Object o)` Removes the first occurrence of the specified element from this deque.
`abstract boolean`	`removeFirstOccurrence(Object o)` Removes the first occurrence of the specified element from this deque.
`abstract boolean`	`removeLastOccurrence(Object o)` Removes the last occurrence of the specified element from this deque.
`abstract int`	`size()` Returns the number of elements in this deque.
`abstract E`	`take()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available.
`abstract E`	`takeFirst()` Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.
`abstract E`	`takeLast()` Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.

From interface


        
          java.lang.Iterable

`default void`	`forEach(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 Iterator<E>`	`iterator()` Returns an iterator over elements of type `T`.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements described by this `Iterable`.

From interface


        
          java.util.concurrent.BlockingQueue

`abstract boolean`	`add(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`	`contains(Object o)` Returns `true` if this queue contains the specified element.
`abstract int`	`drainTo(Collection<? super E> c)` Removes all available elements from this queue and adds them to the given collection.
`abstract 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.
`abstract boolean`	`offer(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`	`offer(E e, long timeout, 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`	`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.
`abstract void`	`put(E e)` Inserts the specified element into this queue, waiting if necessary for space to become available.
`abstract int`	`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`	`remove(Object o)` Removes a single instance of the specified element from this queue, if it is present.
`abstract E`	`take()` Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.

From interface


        
          java.util.Deque

`abstract boolean`	`add(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) 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`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection at the end of this deque, as if by calling `addLast(E)` on each one, in the order that they are returned by the collection's iterator.
`abstract void`	`addFirst(E e)` Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`abstract void`	`addLast(E e)` Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`abstract boolean`	`contains(Object o)` Returns `true` if this deque contains the specified element.
`abstract Iterator<E>`	`descendingIterator()` Returns an iterator over the elements in this deque in reverse sequential order.
`abstract E`	`element()` Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque).
`abstract E`	`getFirst()` Retrieves, but does not remove, the first element of this deque.
`abstract E`	`getLast()` Retrieves, but does not remove, the last element of this deque.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this deque in proper sequence.
`abstract boolean`	`offer(E e)` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) 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`	`offerFirst(E e)` Inserts the specified element at the front of this deque unless it would violate capacity restrictions.
`abstract boolean`	`offerLast(E e)` Inserts the specified element at the end of this deque unless it would violate capacity restrictions.
`abstract E`	`peek()` Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty.
`abstract E`	`peekFirst()` Retrieves, but does not remove, the first element of this deque, or returns `null` if this deque is empty.
`abstract E`	`peekLast()` Retrieves, but does not remove, the last element of this deque, or returns `null` if this deque is empty.
`abstract E`	`poll()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty.
`abstract E`	`pollFirst()` Retrieves and removes the first element of this deque, or returns `null` if this deque is empty.
`abstract E`	`pollLast()` Retrieves and removes the last element of this deque, or returns `null` if this deque is empty.
`abstract E`	`pop()` Pops an element from the stack represented by this deque.
`abstract void`	`push(E e)` Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available.
`abstract E`	`remove()` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque).
`abstract boolean`	`remove(Object o)` Removes the first occurrence of the specified element from this deque.
`abstract E`	`removeFirst()` Retrieves and removes the first element of this deque.
`abstract boolean`	`removeFirstOccurrence(Object o)` Removes the first occurrence of the specified element from this deque.
`abstract E`	`removeLast()` Retrieves and removes the last element of this deque.
`abstract boolean`	`removeLastOccurrence(Object o)` Removes the last occurrence of the specified element from this deque.
`default Deque<E>`	`reversed()` Returns a reverse-ordered view of this collection.
`abstract int`	`size()` Returns the number of elements in this deque.

From interface


        
          java.util.SequencedCollection

`default void`	`addFirst(E e)` Adds an element as the first element of this collection (optional operation).
`default void`	`addLast(E e)` Adds an element as the last element of this collection (optional operation).
`default E`	`getFirst()` Gets the first element of this collection.
`default E`	`getLast()` Gets the last element of this collection.
`default E`	`removeFirst()` Removes and returns the first element of this collection (optional operation).
`default E`	`removeLast()` Removes and returns the last element of this collection (optional operation).
`abstract SequencedCollection<E>`	`reversed()` Returns a reverse-ordered view of this collection.

Public constructors

LinkedBlockingDeque

Added in API level 9

public LinkedBlockingDeque ()

Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE.

LinkedBlockingDeque

Added in API level 9

public LinkedBlockingDeque (int capacity)

Creates a LinkedBlockingDeque with the given (fixed) capacity.

Parameters
`capacity`	`int`: the capacity of this deque

Throws
`IllegalArgumentException`	if `capacity` is less than 1

LinkedBlockingDeque

Added in API level 9

public LinkedBlockingDeque (Collection<? extends E> c)

Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE, initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Parameters
`c`	`Collection`: the collection of elements to initially contain

Throws
`NullPointerException`	if the specified collection or any of its elements are null

Public methods

add

Added in API level 9

public boolean add (E e)

Inserts the specified element at the end of this deque unless it would violate capacity restrictions. When using a capacity-restricted deque, it is generally preferable to use method offer.

This method is equivalent to addLast(E).

Parameters
`e`	`E`: the element to add

Returns
`boolean`	`true` (as specified by `Collection.add`)

Throws
`IllegalStateException`	if this deque is full
`NullPointerException`	if the specified element is null

addAll

Added in API level 9

public boolean addAll (Collection<? extends E> c)

Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator. Attempts to addAll of a deque to itself result in IllegalArgumentException.

Parameters
`c`	`Collection`: the elements to be inserted into this deque

Returns
`boolean`	`true` if this deque changed as a result of the call

Throws
`NullPointerException`	if the specified collection or any of its elements are null
`IllegalArgumentException`	if the collection is this deque
`IllegalStateException`	if this deque is full

See also:

add(Object)

addFirst

Added in API level 9

public void addFirst (E e)

Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offerFirst.

Parameters
`e`	`E`: the element to add

Throws
`IllegalStateException`	if this deque is full
`NullPointerException`

addLast

Added in API level 9

public void addLast (E e)

Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offerLast.

Parameters
`e`	`E`: the element to add

Throws
`IllegalStateException`	if this deque is full
`NullPointerException`

clear

Added in API level 9

public void clear ()

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

contains

Added in API level 9

public boolean contains (Object o)

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

Parameters
`o`	`Object`: object to be checked for containment in this deque

Returns
`boolean`	`true` if this deque contains the specified element

descendingIterator

Added in API level 9

public Iterator<E> descendingIterator ()

Returns an iterator over the elements in this deque in reverse sequential order. The elements will be returned in order from last (tail) to first (head).

The returned iterator is weakly consistent.

Returns
`Iterator<E>`	an iterator over the elements in this deque in reverse order

drainTo

Added in API level 9

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.

Parameters
`c`	`Collection`: the collection to transfer elements into
`maxElements`	`int`: the maximum number of elements to transfer

Returns
`int`	the number of elements transferred

Throws
`UnsupportedOperationException`
`ClassCastException`
`NullPointerException`
`IllegalArgumentException`

drainTo

Added in API level 9

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.

Parameters
`c`	`Collection`: the collection to transfer elements into

Returns
`int`	the number of elements transferred

Throws
`UnsupportedOperationException`
`ClassCastException`
`NullPointerException`
`IllegalArgumentException`

element

Added in API level 9

public E element ()

Retrieves, but does not remove, the head of the queue represented by this deque. This method differs from peek() only in that it throws an exception if this deque is empty.

This method is equivalent to getFirst.

Returns
`E`	the head of the queue represented by this deque

Throws
`NoSuchElementException`	if this deque is empty

forEach

Added in API level 24

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

Parameters
`action`	`Consumer`

Throws
`NullPointerException`

getFirst

Added in API level 9

public E getFirst ()

Retrieves, but does not remove, the first element of this deque. This method differs from peekFirst only in that it throws an exception if this deque is empty.

Returns
`E`	the head of this deque

Throws
`NoSuchElementException`

getLast

Added in API level 9

public E getLast ()

Retrieves, but does not remove, the last element of this deque. This method differs from peekLast only in that it throws an exception if this deque is empty.

Returns
`E`	the tail of this deque

Throws
`NoSuchElementException`

iterator

Added in API level 9

public Iterator<E> iterator ()

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

The returned iterator is weakly consistent.

Returns
`Iterator<E>`	an iterator over the elements in this deque in proper sequence

offer

Added in API level 9

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

Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available.

This method is equivalent to offerLast.

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

Returns
`boolean`	`true` if the element was added to this deque, else `false`

Throws
`NullPointerException`
`InterruptedException`

offer

Added in API level 9

public boolean offer (E e)

Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the add(E) method, which can fail to insert an element only by throwing an exception.

This method is equivalent to offerLast.

Parameters
`e`	`E`: the element to add

Returns
`boolean`	`true` if the element was added to this deque, else `false`

Throws
`NullPointerException`	if the specified element is null

offerFirst

Added in API level 9

public boolean offerFirst (E e)

Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the addFirst method, which can fail to insert an element only by throwing an exception.

Parameters
`e`	`E`: the element to add

Returns
`boolean`	`true` if the element was added to this deque, else `false`

Throws
`NullPointerException`

offerFirst

Added in API level 9

public boolean offerFirst (E e, 
                long timeout, 
                TimeUnit unit)

Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.

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

Returns
`boolean`	`true` if successful, or `false` if the specified waiting time elapses before space is available

Throws
`NullPointerException`
`InterruptedException`

offerLast

Added in API level 9

public boolean offerLast (E e)

Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the addLast method, which can fail to insert an element only by throwing an exception.

Parameters
`e`	`E`: the element to add

Returns
`boolean`	`true` if the element was added to this deque, else `false`

Throws
`NullPointerException`

offerLast

Added in API level 9

public boolean offerLast (E e, 
                long timeout, 
                TimeUnit unit)

Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.

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

Returns
`boolean`	`true` if successful, or `false` if the specified waiting time elapses before space is available

Throws
`NullPointerException`
`InterruptedException`

peek

Added in API level 9

public E peek ()

Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.

This method is equivalent to peekFirst.

Returns
`E`	the head of this deque, or `null` if this deque is empty

peekFirst

Added in API level 9

public E peekFirst ()

Retrieves, but does not remove, the first element of this deque, or returns null if this deque is empty.

Returns
`E`	the head of this deque, or `null` if this deque is empty

peekLast

Added in API level 9

public E peekLast ()

Retrieves, but does not remove, the last element of this deque, or returns null if this deque is empty.

Returns
`E`	the tail of this deque, or `null` if this deque is empty

poll

Added in API level 9

public E poll (long timeout, 
                TimeUnit unit)

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available.

This method is equivalent to pollFirst.

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

Returns
`E`	the head of this deque, or `null` if the specified waiting time elapses before an element is available

Throws
`InterruptedException`

poll

Added in API level 9

public E poll ()

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.

This method is equivalent to Deque.pollFirst().

Returns
`E`	the head of this deque, or `null` if this deque is empty

pollFirst

Added in API level 9

public E pollFirst ()

Retrieves and removes the first element of this deque, or returns null if this deque is empty.

Returns
`E`	the head of this deque, or `null` if this deque is empty

pollFirst

Added in API level 9

public E pollFirst (long timeout, 
                TimeUnit unit)

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

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

Returns
`E`	the head of this deque, or `null` if the specified waiting time elapses before an element is available

Throws
`InterruptedException`

pollLast

Added in API level 9

public E pollLast ()

Retrieves and removes the last element of this deque, or returns null if this deque is empty.

Returns
`E`	the tail of this deque, or `null` if this deque is empty

pollLast

Added in API level 9

public E pollLast (long timeout, 
                TimeUnit unit)

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

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

Returns
`E`	the tail of this deque, or `null` if the specified waiting time elapses before an element is available

Throws
`InterruptedException`

pop

Added in API level 9

public E pop ()

Pops an element from the stack represented by this deque. In other words, removes and returns the first element of this deque.

This method is equivalent to removeFirst().

Returns
`E`	the element at the front of this deque (which is the top of the stack represented by this deque)

Throws
`NoSuchElementException`

push

Added in API level 9

public void push (E e)

Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available.

This method is equivalent to addFirst.

Parameters
`e`	`E`: the element to push

Throws
`IllegalStateException`	if this deque is full
`NullPointerException`

put

Added in API level 9

public void put (E e)

Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.

This method is equivalent to putLast.

Parameters
`e`	`E`: the element to add

Throws
`NullPointerException`
`InterruptedException`

putFirst

Added in API level 9

public void putFirst (E e)

Inserts the specified element at the front of this deque, waiting if necessary for space to become available.

Parameters
`e`	`E`: the element to add

Throws
`NullPointerException`
`InterruptedException`

putLast

Added in API level 9

public void putLast (E e)

Inserts the specified element at the end of this deque, waiting if necessary for space to become available.

Parameters
`e`	`E`: the element to add

Throws
`NullPointerException`
`InterruptedException`

remainingCapacity

Added in API level 9

public int remainingCapacity ()

Returns the number of additional elements that this deque can ideally (in the absence of memory or resource constraints) accept without blocking. This is always equal to the initial capacity of this deque less the current size of this deque.

Note that you cannot always tell if an attempt to insert an element will succeed by inspecting remainingCapacity because it may be the case that another thread is about to insert or remove an element.

Returns
`int`	the remaining capacity

remove

Added in API level 9

public boolean remove (Object o)

Removes the first occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the first element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).

This method is equivalent to removeFirstOccurrence.

Parameters
`o`	`Object`: element to be removed from this deque, if present

Returns
`boolean`	`true` if this deque changed as a result of the call

remove

Added in API level 9

public E remove ()

Retrieves and removes the head of the queue represented by this deque. This method differs from poll() only in that it throws an exception if this deque is empty.

This method is equivalent to removeFirst.

Returns
`E`	the head of the queue represented by this deque

Throws
`NoSuchElementException`	if this deque is empty

removeAll

Added in API level 9

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.

Parameters
`c`	`Collection`: collection containing elements to be removed from this collection

Returns
`boolean`	`true` if this collection changed as a result of the call

Throws
`NullPointerException`

removeFirst

Added in API level 9

public E removeFirst ()

Retrieves and removes the first element of this deque. This method differs from pollFirst only in that it throws an exception if this deque is empty.

Returns
`E`	the head of this deque

Throws
`NoSuchElementException`

removeFirstOccurrence

Added in API level 9

public boolean removeFirstOccurrence (Object o)

Parameters
`o`	`Object`: element to be removed from this deque, if present

Returns
`boolean`	`true` if an element was removed as a result of this call

removeIf

Added in API level 24

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

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

Parameters
`filter`	`Predicate`: a predicate which returns `true` for elements to be removed

Returns
`boolean`	`true` if any elements were removed

Throws
`NullPointerException`

removeLast

Added in API level 9

public E removeLast ()

Retrieves and removes the last element of this deque. This method differs from pollLast only in that it throws an exception if this deque is empty.

Returns
`E`	the tail of this deque

Throws
`NoSuchElementException`

removeLastOccurrence

Added in API level 9

public boolean removeLastOccurrence (Object o)

Removes the last occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the last element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).

Parameters
`o`	`Object`: element to be removed from this deque, if present

Returns
`boolean`	`true` if an element was removed as a result of this call

retainAll

Added in API level 9

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.

Parameters
`c`	`Collection`: collection containing elements to be retained in this collection

Returns
`boolean`	`true` if this collection changed as a result of the call

Throws
`NullPointerException`

size

Added in API level 9

public int size ()

Returns the number of elements in this deque.

Returns
`int`	the number of elements in this deque

spliterator

Added in API level 24

public Spliterator<E> spliterator ()

Returns a Spliterator over the elements in this deque.

The returned spliterator is weakly consistent.

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

Implementation Note:

The Spliterator implements trySplit to permit limited parallelism.

Returns
`Spliterator<E>`	a `Spliterator` over the elements in this deque

take

Added in API level 9

public E take ()

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available.

This method is equivalent to takeFirst.

Returns
`E`	the head of this deque

Throws
`InterruptedException`

takeFirst

Added in API level 9

public E takeFirst ()

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

Returns
`E`	the head of this deque

Throws
`InterruptedException`

takeLast

Added in API level 9

public E takeLast ()

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

Returns
`E`	the tail of this deque

Throws
`InterruptedException`

toArray

Added in API level 9

public Object[] toArray ()

Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).

The returned array will be "safe" in that no references to it are maintained by this deque. (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.

Returns
`Object[]`	an array containing all of the elements in this deque

toArray

Added in API level 9

public T[] toArray (T[] a)

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

If this deque fits in the specified array with room to spare (i.e., the array has more elements than this deque), the element in the array immediately following the end of the deque is set to null.

Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.

Suppose x is a deque known to contain only strings. The following code can be used to dump the deque 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().

Parameters
`a`	`T`: the array into which the elements of the deque are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose

Returns
`T[]`	an array containing all of the elements in this deque

Throws
`ArrayStoreException`	if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque
`NullPointerException`	if the specified array is null

toString

Added in API level 9

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 String.valueOf(Object).

Returns
`String`	a string representation of this collection