Module java.base

Package java.util.concurrent

Class LinkedBlockingDeque<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

java.util.concurrent.LinkedBlockingDeque<E>

Type Parameters:

E - the type of elements held in this deque

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, BlockingDeque<E>, BlockingQueue<E>, Deque<E>, Queue<E>, SequencedCollection<E>

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

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.

Since:

1.6

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
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.

Method Summary

Modifier and Type	Method	Description
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)	Removes all available elements from this queue and adds them to the given collection.
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.
E	element()	Retrieves, but does not remove, the head of the queue represented by this deque.
void	forEach(Consumer<? super E> action)	Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
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)	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	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	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()	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	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	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.
E	remove()	Retrieves and removes the head of the queue represented by this deque.
boolean	remove(Object o)	Removes the first occurrence of the specified element from 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 (optional operation).
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.

Methods declared in class java.util.AbstractCollection

containsAll, isEmpty, toString

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods declared in interface java.util.Collection

containsAll, equals, hashCode, isEmpty, parallelStream, stream, toArray

Methods declared in interface java.util.Deque

reversed

Constructor Details

LinkedBlockingDeque

public LinkedBlockingDeque()

Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE.

LinkedBlockingDeque

public LinkedBlockingDeque(int capacity)

Creates a LinkedBlockingDeque with the given (fixed) capacity.

Parameters:

capacity - the capacity of this deque

Throws:

IllegalArgumentException - if capacity is less than 1

LinkedBlockingDeque

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 - the collection of elements to initially contain

Throws:

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

Method Details

addFirst

public void addFirst(E e)

Description copied from interface: BlockingDeque

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.

Specified by:

addFirst in interface BlockingDeque<E>

Specified by:

addFirst in interface Deque<E>

Specified by:

addFirst in interface SequencedCollection<E>

Parameters:

e - the element to add

Throws:

IllegalStateException - if this deque is full

NullPointerException - if the specified element is null

addLast

public void addLast(E e)

Description copied from interface: BlockingDeque

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.

Specified by:

addLast in interface BlockingDeque<E>

Specified by:

addLast in interface Deque<E>

Specified by:

addLast in interface SequencedCollection<E>

Parameters:

e - the element to add

Throws:

IllegalStateException - if this deque is full

NullPointerException - if the specified element is null

offerFirst

public boolean offerFirst(E e)

Description copied from interface: BlockingDeque

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.

Specified by:

offerFirst in interface BlockingDeque<E>

Specified by:

offerFirst in interface Deque<E>

Parameters:

e - the element to add

Returns:

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

Throws:

NullPointerException - if the specified element is null

offerLast

public boolean offerLast(E e)

Description copied from interface: BlockingDeque

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.

Specified by:

offerLast in interface BlockingDeque<E>

Specified by:

offerLast in interface Deque<E>

Parameters:

e - the element to add

Returns:

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

Throws:

NullPointerException - if the specified element is null

putFirst

public void putFirst(E e)
              throws InterruptedException

Description copied from interface: BlockingDeque

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

Specified by:

putFirst in interface BlockingDeque<E>

Parameters:

e - the element to add

Throws:

NullPointerException - if the specified element is null

InterruptedException - if interrupted while waiting

putLast

public void putLast(E e)
             throws InterruptedException

Description copied from interface: BlockingDeque

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

Specified by:

putLast in interface BlockingDeque<E>

Parameters:

e - the element to add

Throws:

NullPointerException - if the specified element is null

InterruptedException - if interrupted while waiting

offerFirst

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

Description copied from interface: BlockingDeque

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

Specified by:

offerFirst in interface BlockingDeque<E>

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:

NullPointerException - if the specified element is null

InterruptedException - if interrupted while waiting

offerLast

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

Description copied from interface: BlockingDeque

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

Specified by:

offerLast in interface BlockingDeque<E>

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:

NullPointerException - if the specified element is null

InterruptedException - if interrupted while waiting

removeFirst

public E removeFirst()

Description copied from interface: Deque

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.

Specified by:

removeFirst in interface Deque<E>

Specified by:

removeFirst in interface SequencedCollection<E>

Returns:

the head of this deque

Throws:

NoSuchElementException - if this deque is empty

removeLast

public E removeLast()

Description copied from interface: Deque

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.

Specified by:

removeLast in interface Deque<E>

Specified by:

removeLast in interface SequencedCollection<E>

Returns:

the tail of this deque

Throws:

NoSuchElementException - if this deque is empty

pollFirst

public E pollFirst()

Description copied from interface: Deque

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

Specified by:

pollFirst in interface Deque<E>

Returns:

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

pollLast

public E pollLast()

Description copied from interface: Deque

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

Specified by:

pollLast in interface Deque<E>

Returns:

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

takeFirst

public E takeFirst()
            throws InterruptedException

Description copied from interface: BlockingDeque

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

Specified by:

takeFirst in interface BlockingDeque<E>

Returns:

the head of this deque

Throws:

InterruptedException - if interrupted while waiting

takeLast

public E takeLast()
           throws InterruptedException

Description copied from interface: BlockingDeque

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

Specified by:

takeLast in interface BlockingDeque<E>

Returns:

the tail of this deque

Throws:

InterruptedException - if interrupted while waiting

pollFirst

public E pollFirst(long timeout,
 TimeUnit unit)
            throws InterruptedException

Description copied from interface: BlockingDeque

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

Specified by:

pollFirst in interface BlockingDeque<E>

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

pollLast

public E pollLast(long timeout,
 TimeUnit unit)
           throws InterruptedException

Description copied from interface: BlockingDeque

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

Specified by:

pollLast in interface BlockingDeque<E>

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

getFirst

public E getFirst()

Description copied from interface: Deque

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.

Specified by:

getFirst in interface Deque<E>

Specified by:

getFirst in interface SequencedCollection<E>

Returns:

the head of this deque

Throws:

NoSuchElementException - if this deque is empty

getLast

public E getLast()

Description copied from interface: Deque

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.

Specified by:

getLast in interface Deque<E>

Specified by:

getLast in interface SequencedCollection<E>

Returns:

the tail of this deque

Throws:

NoSuchElementException - if this deque is empty

peekFirst

public E peekFirst()

Description copied from interface: Deque

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

Specified by:

peekFirst in interface Deque<E>

Returns:

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

peekLast

public E peekLast()

Description copied from interface: Deque

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

Specified by:

peekLast in interface Deque<E>

Returns:

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

removeFirstOccurrence

public boolean removeFirstOccurrence(Object o)

Description copied from interface: BlockingDeque

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).

Specified by:

removeFirstOccurrence in interface BlockingDeque<E>

Specified by:

removeFirstOccurrence in interface Deque<E>

Parameters:

o - element to be removed from this deque, if present

Returns:

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

removeLastOccurrence

public boolean removeLastOccurrence(Object o)

Description copied from interface: BlockingDeque

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).

Specified by:

removeLastOccurrence in interface BlockingDeque<E>

Specified by:

removeLastOccurrence in interface Deque<E>

Parameters:

o - element to be removed from this deque, if present

Returns:

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

add

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).

Specified by:

add in interface BlockingDeque<E>

Specified by:

add in interface BlockingQueue<E>

Specified by:

add in interface Collection<E>

Specified by:

add in interface Deque<E>

Specified by:

add in interface Queue<E>

Overrides:

add in class AbstractQueue<E>

Parameters:

e - the element to add

Returns:

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

Throws:

IllegalStateException - if this deque is full

NullPointerException - if the specified element is null

offer

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 BlockingDeque.add(E) method, which can fail to insert an element only by throwing an exception.

This method is equivalent to offerLast.

Specified by:

offer in interface BlockingDeque<E>

Specified by:

offer in interface BlockingQueue<E>

Specified by:

offer in interface Deque<E>

Specified by:

offer in interface Queue<E>

Parameters:

e - the element to add

Returns:

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

Throws:

NullPointerException - if the specified element is null

put

public void put(E e)
         throws InterruptedException

Description copied from interface: BlockingDeque

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.

Specified by:

put in interface BlockingDeque<E>

Specified by:

put in interface BlockingQueue<E>

Parameters:

e - the element to add

Throws:

NullPointerException - if the specified element is null

InterruptedException - if interrupted while waiting

offer

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

Description copied from interface: BlockingDeque

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.

Specified by:

offer in interface BlockingDeque<E>

Specified by:

offer in interface BlockingQueue<E>

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:

NullPointerException - if the specified element is null

InterruptedException - if interrupted while waiting

remove

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.

Specified by:

remove in interface BlockingDeque<E>

Specified by:

remove in interface Deque<E>

Specified by:

remove in interface Queue<E>

Overrides:

remove in class AbstractQueue<E>

Returns:

the head of the queue represented by this deque

Throws:

NoSuchElementException - if this deque is empty

poll

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().

Specified by:

poll in interface BlockingDeque<E>

Specified by:

poll in interface Deque<E>

Specified by:

poll in interface Queue<E>

Returns:

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

take

public E take()
       throws InterruptedException

Description copied from interface: BlockingDeque

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.

Specified by:

take in interface BlockingDeque<E>

Specified by:

take in interface BlockingQueue<E>

Returns:

the head of this deque

Throws:

InterruptedException - if interrupted while waiting

poll

public E poll(long timeout,
 TimeUnit unit)
       throws InterruptedException

Description copied from interface: BlockingDeque

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.

Specified by:

poll in interface BlockingDeque<E>

Specified by:

poll in interface BlockingQueue<E>

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

element

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.

Specified by:

element in interface BlockingDeque<E>

Specified by:

element in interface Deque<E>

Specified by:

element in interface Queue<E>

Overrides:

element in class AbstractQueue<E>

Returns:

the head of the queue represented by this deque

Throws:

NoSuchElementException - if this deque is empty

peek

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.

Specified by:

peek in interface BlockingDeque<E>

Specified by:

peek in interface Deque<E>

Specified by:

peek in interface Queue<E>

Returns:

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

remainingCapacity

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.

Specified by:

remainingCapacity in interface BlockingQueue<E>

Returns:

the remaining capacity

drainTo

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

Description copied from interface: BlockingQueue

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.

Specified by:

drainTo in interface BlockingQueue<E>

Parameters:

c - the collection to transfer elements into

Returns:

the number of elements transferred

Throws:

UnsupportedOperationException - if addition of elements is not supported by the specified collection

ClassCastException - if the class of an element of this queue prevents it from being added to the specified collection

NullPointerException - if the specified collection is null

IllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

drainTo

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

Description copied from interface: BlockingQueue

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.

Specified by:

drainTo in interface BlockingQueue<E>

Parameters:

c - the collection to transfer elements into

maxElements - the maximum number of elements to transfer

Returns:

the number of elements transferred

Throws:

UnsupportedOperationException - if addition of elements is not supported by the specified collection

ClassCastException - if the class of an element of this queue prevents it from being added to the specified collection

NullPointerException - if the specified collection is null

IllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

push

public void push(E e)

Description copied from interface: BlockingDeque

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.

Specified by:

push in interface BlockingDeque<E>

Specified by:

push in interface Deque<E>

Parameters:

e - the element to push

Throws:

IllegalStateException - if this deque is full

NullPointerException - if the specified element is null

pop

public E pop()

Description copied from interface: Deque

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 Deque.removeFirst().

Specified by:

pop in interface Deque<E>

Returns:

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

Throws:

NoSuchElementException - if this deque is empty

remove

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.

Specified by:

remove in interface BlockingDeque<E>

Specified by:

remove in interface BlockingQueue<E>

Specified by:

remove in interface Collection<E>

Specified by:

remove in interface Deque<E>

Overrides:

remove in class AbstractCollection<E>

Parameters:

o - element to be removed from this deque, if present

Returns:

true if this deque changed as a result of the call

size

public int size()

Returns the number of elements in this deque.

Specified by:

size in interface BlockingDeque<E>

Specified by:

size in interface Collection<E>

Specified by:

size in interface Deque<E>

Returns:

the number of elements in this deque

contains

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).

Specified by:

contains in interface BlockingDeque<E>

Specified by:

contains in interface BlockingQueue<E>

Specified by:

contains in interface Collection<E>

Specified by:

contains in interface Deque<E>

Overrides:

contains in class AbstractCollection<E>

Parameters:

o - object to be checked for containment in this deque

Returns:

true if this deque contains the specified element

addAll

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.

Specified by:

addAll in interface Collection<E>

Specified by:

addAll in interface Deque<E>

Overrides:

addAll in class AbstractQueue<E>

Parameters:

c - the elements to be inserted into this deque

Returns:

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)

toArray

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.

Specified by:

toArray in interface Collection<E>

Overrides:

toArray in class AbstractCollection<E>

Returns:

an array containing all of the elements in this deque

toArray

public <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. 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().

Specified by:

toArray in interface Collection<E>

Overrides:

toArray in class AbstractCollection<E>

Type Parameters:

T - the component type of the array to contain the collection

Parameters:

a - 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:

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

clear

public void clear()

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

Specified by:

clear in interface Collection<E>

Overrides:

clear in class AbstractQueue<E>

iterator

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.

Specified by:

iterator in interface BlockingDeque<E>

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Deque<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in class AbstractCollection<E>

Returns:

an iterator over the elements in this deque in proper sequence

descendingIterator

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.

Specified by:

descendingIterator in interface Deque<E>

Returns:

an iterator over the elements in this deque in reverse order

spliterator

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.

Specified by:

spliterator in interface Collection<E>

Specified by:

spliterator in interface Iterable<E>

Implementation Note:

The Spliterator implements trySplit to permit limited parallelism.

Returns:

a Spliterator over the elements in this deque

Since:

1.8

forEach

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

Description copied from interface: Iterable

Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller.

The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy.

Specified by:

forEach in interface Iterable<E>

Parameters:

action - The action to be performed for each element

Throws:

NullPointerException - if the specified action is null

removeIf

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

Description copied from interface: Collection

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

Specified by:

removeIf in interface Collection<E>

Parameters:

filter - a predicate which returns true for elements to be removed

Returns:

true if any elements were removed

Throws:

NullPointerException - if the specified filter is null

removeAll

public boolean removeAll(Collection<?> c)

Description copied from class: AbstractCollection

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.

Specified by:

removeAll in interface Collection<E>

Overrides:

removeAll in class AbstractCollection<E>

Parameters:

c - collection containing elements to be removed from this collection

Returns:

true if this collection changed as a result of the call

Throws:

NullPointerException - if this collection contains one or more null elements and the specified collection does not support null elements (optional) or if the specified collection is null

See Also:

• AbstractCollection.remove(Object)
• AbstractCollection.contains(Object)

retainAll

public boolean retainAll(Collection<?> c)

Description copied from class: AbstractCollection

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.

Specified by:

retainAll in interface Collection<E>

Overrides:

retainAll in class AbstractCollection<E>

Parameters:

c - collection containing elements to be retained in this collection

Returns:

true if this collection changed as a result of the call

Throws:

NullPointerException - if this collection contains one or more null elements and the specified collection does not permit null elements (optional) or if the specified collection is null

See Also:

• AbstractCollection.remove(Object)
• AbstractCollection.contains(Object)