BlockingDeque

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

Known Indirect Subclasses

LinkedBlockingDeque<E>

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()`
`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.

Public Method Summary

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 Method Summary

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 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.
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.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.
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).
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.
Spliterator<E>	spliterator() Creates a `Spliterator` over the elements in this collection.
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.

From interface java.lang.Iterable

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`.
Spliterator<E>	spliterator() Creates a `Spliterator` over the elements described by this `Iterable`.

Public Methods

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	the element to add

Returns

true (as specified by Collection.add(E))

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

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	the element to add

Throws

IllegalStateException
ClassCastException
NullPointerException	if the specified element is null
IllegalArgumentException

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	the element to add

Throws

IllegalStateException
ClassCastException
NullPointerException	if the specified element is null
IllegalArgumentException

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 to be checked for containment in this deque

Returns

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)

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

the head of this deque

Throws

NoSuchElementException	if this deque is empty

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

an iterator over the elements in this deque in proper sequence

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

Returns

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

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	the element to add

Returns

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

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	the element to add

Returns

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

Throws

ClassCastException
NullPointerException	if the specified element is null
IllegalArgumentException

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

Returns

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

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	the element to add

Returns

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

Throws

ClassCastException
NullPointerException	if the specified element is null
IllegalArgumentException

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

Returns

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

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

the head of this deque, or null if this deque is empty

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

Returns

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

Throws

InterruptedException	if interrupted while waiting

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

the head of this deque, or null if this deque is empty

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

Returns

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

Throws

InterruptedException	if interrupted while waiting

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

Returns

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

Throws

InterruptedException	if interrupted while waiting

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	the element to push

Throws

IllegalStateException
ClassCastException
NullPointerException	if the specified element is null
IllegalArgumentException

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	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

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	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

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	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

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

the head of the queue represented by this deque

Throws

NoSuchElementException	if this deque is empty

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	element to be removed from this deque, if present

Returns

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)

public abstract boolean removeFirstOccurrence (Object o)

Parameters

o	element to be removed from this deque, if present

Returns

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)

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	element to be removed from this deque, if present

Returns

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)

public abstract int size ()

Returns the number of elements in this deque.

Returns

the number of elements in this deque

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

the head of this deque

Throws

InterruptedException	if interrupted while waiting

public abstract E takeFirst ()

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

Returns

the head of this deque

Throws

InterruptedException	if interrupted while waiting

public abstract E takeLast ()

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

Returns

the tail of this deque

Throws

InterruptedException	if interrupted while waiting