Added in API level 9

Summary: Methods | Inherited Methods

BlockingDeque

public interface BlockingDeque
implements BlockingQueue<E>, Deque<E>

java.util.concurrent.BlockingDeque<E>

Known indirect subclasses

LinkedBlockingDeque<E> An optionally-bounded blocking deque based on linked nodes.

A Deque that additionally supports blocking operations that wait for the deque to become non-empty when retrieving an element, and wait for space to become available in the deque when storing an element.

BlockingDeque methods come in four forms, with different ways of handling operations that cannot be satisfied immediately, but may be satisfied at some point in the future: one throws an exception, the second returns a special value (either null or false, depending on the operation), the third blocks the current thread indefinitely until the operation can succeed, and the fourth blocks for only a given maximum time limit before giving up. These methods are summarized in the following table:

Summary of BlockingDeque methods
First Element (Head)
	Throws exception	Special value	Blocks	Times out
Insert	`addFirst(e)`	`offerFirst(e)`	`putFirst(e)`	`offerFirst(e, time, unit)`
Remove	`removeFirst()`	`pollFirst()`	`takeFirst()`	`pollFirst(time, unit)`
Examine	`getFirst()`	`peekFirst()`	not applicable	not applicable
Last Element (Tail)
	Throws exception	Special value	Blocks	Times out
Insert	`addLast(e)`	`offerLast(e)`	`putLast(e)`	`offerLast(e, time, unit)`
Remove	`removeLast()`	`pollLast()`	`takeLast()`	`pollLast(time, unit)`
Examine	`getLast()`	`peekLast()`	not applicable	not applicable

Like any BlockingQueue, a BlockingDeque is thread safe, does not permit null elements, and may (or may not) be capacity-constrained.

A BlockingDeque implementation may be used directly as a FIFO BlockingQueue. The methods inherited from the BlockingQueue interface are precisely equivalent to BlockingDeque methods as indicated in the following table:

Comparison of BlockingQueue and BlockingDeque methods
	`BlockingQueue` Method	Equivalent `BlockingDeque` Method
Insert	`add(e)`	`addLast(e)`
	`offer(e)`	`offerLast(e)`
	`put(e)`	`putLast(e)`
	`offer(e, time, unit)`	`offerLast(e, time, unit)`
Remove	`remove()`	`removeFirst()`
	`poll()`	`pollFirst()`
	`take()`	`takeFirst()`
	`poll(time, unit)`	`pollFirst(time, unit)`
Examine	`element()`	`getFirst()`
Examine	`peek()`	`peekFirst()`

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

This interface is a member of the Java Collections Framework.

Summary

Public methods
`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.

Inherited methods

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.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.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.

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.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`.

Public methods

add

Added in API level 9

public 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. When using a capacity-restricted deque, it is generally preferable to use offer.

This method is equivalent to addLast.

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

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

Throws
`IllegalStateException`
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

addFirst

Added in API level 9

public 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. When using a capacity-restricted deque, it is generally preferable to use offerFirst.

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

Throws
`IllegalStateException`
`ClassCastException`
`NullPointerException`	if the specified element is null
`IllegalArgumentException`

addLast

Added in API level 9

public 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. When using a capacity-restricted deque, it is generally preferable to use offerLast.

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

Throws
`IllegalStateException`
`ClassCastException`
`NullPointerException`	if the specified element is null
`IllegalArgumentException`

contains

Added in API level 9

public abstract 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

Throws
`ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`NullPointerException`	if the specified element is null (optional)

element

Added in API level 9

public 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). 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 this deque

Throws
`NoSuchElementException`	if this deque is empty

iterator

Added in API level 9

public abstract 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).

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

offer

Added in API level 9

public 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.

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
`InterruptedException`
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

offer

Added in API level 9

public 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. 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
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

offerFirst

Added in API level 9

public 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. 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
`ClassCastException`
`NullPointerException`	if the specified element is null
`IllegalArgumentException`

offerFirst

Added in API level 9

public 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.

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
`InterruptedException`	if interrupted while waiting
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

offerLast

Added in API level 9

public 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. 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
`ClassCastException`
`NullPointerException`	if the specified element is null
`IllegalArgumentException`

offerLast

Added in API level 9

public 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.

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
`InterruptedException`	if interrupted while waiting
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

peek

Added in API level 9

public 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.

This method is equivalent to peekFirst.

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

poll

Added in API level 9

public 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.

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`	if interrupted while waiting

poll

Added in API level 9

public 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.

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 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.

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`	if interrupted while waiting

pollLast

Added in API level 9

public 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.

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`	if interrupted while waiting

push

Added in API level 9

public 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.

This method is equivalent to addFirst.

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

Throws
`IllegalStateException`
`ClassCastException`
`NullPointerException`	if the specified element is null
`IllegalArgumentException`

put

Added in API level 9

public 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.

This method is equivalent to putLast.

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

Throws
`InterruptedException`
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

putFirst

Added in API level 9

public abstract 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
`InterruptedException`	if interrupted while waiting
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

putLast

Added in API level 9

public abstract 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
`InterruptedException`	if interrupted while waiting
`ClassCastException`	if the class of the specified element prevents it from being added to this deque
`NullPointerException`	if the specified element is null
`IllegalArgumentException`	if some property of the specified element prevents it from being added to this deque

remove

Added in API level 9

public abstract E remove ()

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of 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

remove

Added in API level 9

public abstract 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

Throws
`ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`NullPointerException`	if the specified element is null (optional)

removeFirstOccurrence

Added in API level 9

public abstract 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

Throws
`ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`NullPointerException`	if the specified element is null (optional)

removeLastOccurrence

Added in API level 9

public abstract 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

Throws
`ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`NullPointerException`	if the specified element is null (optional)

size

Added in API level 9

public abstract int size ()

Returns the number of elements in this deque.

Returns
`int`	the number of elements in this deque

take

Added in API level 9

public 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.

This method is equivalent to takeFirst.

Returns
`E`	the head of this deque

Throws
`InterruptedException`	if interrupted while waiting

takeFirst

Added in API level 9

public abstract 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`	if interrupted while waiting

takeLast

Added in API level 9

public abstract 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`	if interrupted while waiting