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:

  • 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.
    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)
      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) 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()
      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), 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()
      Description copied from interface: BlockingDeque
      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:

    • 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. 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:

    • 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: