Package org.apache.commons.pool2.impl

Class LinkedBlockingDeque<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
org.apache.commons.pool2.impl.LinkedBlockingDeque<E>
Type Parameters:
E - the type of elements held in this collection Note: This was copied from Apache Harmony and modified to suit the needs of Commons Pool.
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, BlockingDeque<E>, BlockingQueue<E>, Deque<E>, Queue<E>
final 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:
2.0

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    private class 
    LinkedBlockingDeque.AbstractItr
    Base class for Iterators for LinkedBlockingDeque
    private final class 
    LinkedBlockingDeque.DescendingItr
    Descending iterator
    private final class 
    LinkedBlockingDeque.Itr
    Forward iterator
    private static final class 
    LinkedBlockingDeque.Node<E>
    Doubly-linked list node class.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final int
    capacity
    Maximum number of items in the deque
    private int
    count
    Number of items in the deque
    private LinkedBlockingDeque.Node<E>
    first
    Pointer to first node.
    private LinkedBlockingDeque.Node<E>
    last
    Pointer to last node.
    private final InterruptibleReentrantLock
    lock
    Main lock guarding all access
    private final Condition
    notEmpty
    Condition for waiting takes
    private final Condition
    notFull
    Condition for waiting puts
    private static final long
    serialVersionUID
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    LinkedBlockingDeque()
    Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE.
    LinkedBlockingDeque(boolean fairness)
    Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE and the given fairness policy.
    LinkedBlockingDeque(int capacity)
    Creates a LinkedBlockingDeque with the given (fixed) capacity.
    LinkedBlockingDeque(int capacity, boolean fairness)
    Creates a LinkedBlockingDeque with the given (fixed) capacity and fairness policy.
    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)
    void
    addFirst(E e)
    void
    addLast(E e)
    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()
    int
    drainTo(Collection<? super E> c)
    Drains the queue to the specified collection.
    int
    drainTo(Collection<? super E> collection, int maxElements)
    Drains no more than the specified number of elements from the queue to the specified collection.
    E
    element()
    Retrieves, but does not remove, the head of the queue represented by this deque.
    E
    getFirst()
    E
    getLast()
    (package private) int
    getTakeQueueLength()
    Gets the length of the queue of threads waiting to take instances from this deque.
    (package private) boolean
    hasTakeWaiters()
    Returns true if there are threads waiting to take instances from this deque.
    (package private) void
    interruptTakeWaiters()
    Interrupts the threads currently waiting to take an object from the pool.
    Iterator<E>
    iterator()
    Returns an iterator over the elements in this deque in proper sequence.
    private boolean
    linkFirst(E e)
    Links provided element as first element, or returns false if full.
    private boolean
    linkLast(E e)
    Links provided element as last element, or returns false if full.
    boolean
    offer(E e)
    boolean
    offer(E e, long timeout, TimeUnit unit)
    Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.
    (package private) boolean
    offer(E e, Duration timeout)
    Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.
    boolean
    offerFirst(E e)
    boolean
    offerFirst(E e, long timeout, TimeUnit unit)
    Links the provided element as the first in the queue, waiting up to the specified time to do so if the queue is full.
    (package private) boolean
    offerFirst(E e, Duration timeout)
    Links the provided element as the first in the queue, waiting up to the specified time to do so if the queue is full.
    boolean
    offerLast(E e)
    boolean
    offerLast(E e, long timeout, TimeUnit unit)
    Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.
    (package private) boolean
    offerLast(E e, Duration timeout)
    Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.
    E
    peek()
     
    E
    peekFirst()
     
    E
    peekLast()
     
    E
    poll()
     
    E
    poll(long timeout, TimeUnit unit)
    Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.
    (package private) E
    poll(Duration timeout)
    Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.
    E
    pollFirst()
     
    E
    pollFirst(long timeout, TimeUnit unit)
    Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.
    (package private) E
    pollFirst(Duration timeout)
    Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.
    E
    pollLast()
     
    E
    pollLast(long timeout, TimeUnit unit)
    Unlinks the last element in the queue, waiting up to the specified time to do so if the queue is empty.
    (package private) E
    pollLast(Duration timeout)
    Unlinks the last element in the queue, waiting up to the specified time to do so if the queue is empty.
    E
    pop()
    void
    push(E e)
    void
    put(E e)
    Links the provided element as the last in the queue, waiting until there is space to do so if the queue is full.
    void
    putFirst(E e)
    Links the provided element as the first in the queue, waiting until there is space to do so if the queue is full.
    void
    putLast(E e)
    Links the provided element as the last in the queue, waiting until there is space to do so if the queue is full.
    private void
    readObject(ObjectInputStream s)
    Reconstitutes this deque from a stream (that is, deserialize it).
    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.
    E
    removeFirst()
    boolean
    removeFirstOccurrence(Object o)
     
    E
    removeLast()
    boolean
    removeLastOccurrence(Object o)
     
    int
    size()
    Returns the number of elements in this deque.
    E
    take()
    Unlinks the first element in the queue, waiting until there is an element to unlink if the queue is empty.
    E
    takeFirst()
    Unlinks the first element in the queue, waiting until there is an element to unlink if the queue is empty.
    E
    takeLast()
    Unlinks the last element in the queue, waiting until there is an element to unlink if the queue is empty.
    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)
    String
    toString()
     
    private void
    unlink(LinkedBlockingDeque.Node<E> x)
    Unlinks the provided node.
    private E
    unlinkFirst()
    Removes and returns the first element, or null if empty.
    private E
    unlinkLast()
    Removes and returns the last element, or null if empty.
    private void
    writeObject(ObjectOutputStream s)
    Saves the state of this deque to a stream (that is, serialize it).

    Methods inherited from class java.util.AbstractQueue

    addAll

    Methods inherited from class java.util.AbstractCollection

    containsAll, isEmpty, removeAll, retainAll

    Methods inherited from class java.lang.Object

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

    Methods inherited from interface java.util.Collection

    addAll, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream

    Methods inherited from interface java.lang.Iterable

    forEach

  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      See Also:

    • first

      private transient LinkedBlockingDeque.Node<E> first
      Pointer to first node. Invariant: (first == null invalid input: '&'invalid input: '&' last == null) || (first.prev == null invalid input: '&'invalid input: '&' first.item != null)

    • last

      private transient LinkedBlockingDeque.Node<E> last
      Pointer to last node. Invariant: (first == null invalid input: '&'invalid input: '&' last == null) || (last.next == null invalid input: '&'invalid input: '&' last.item != null)

    • count

      private transient int count
      Number of items in the deque

    • capacity

      private final int capacity
      Maximum number of items in the deque

    • lock

      private final InterruptibleReentrantLock lock
      Main lock guarding all access

    • notEmpty

      private final Condition notEmpty
      Condition for waiting takes

    • notFull

      private final Condition notFull
      Condition for waiting puts

  • Constructor Details

    • LinkedBlockingDeque

      LinkedBlockingDeque()
      Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE.

    • LinkedBlockingDeque

      LinkedBlockingDeque(boolean fairness)
      Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE and the given fairness policy.
      Parameters:
      fairness - true means threads waiting on the deque should be served as if waiting in a FIFO request queue

    • LinkedBlockingDeque

      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

    • LinkedBlockingDeque

      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

      LinkedBlockingDeque(int capacity, boolean fairness)
      Creates a LinkedBlockingDeque with the given (fixed) capacity and fairness policy.
      Parameters:
      capacity - the capacity of this deque
      fairness - true means threads waiting on the deque should be served as if waiting in a FIFO request queue
      Throws:
      IllegalArgumentException - if capacity is less than 1

  • Method Details

    • add

      public boolean add(E 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>

    • addFirst

      public void addFirst(E e)
      Specified by:
      addFirst in interface BlockingDeque<E>
      Specified by:
      addFirst in interface Deque<E>

    • addLast

      public void addLast(E e)
      Specified by:
      addLast in interface BlockingDeque<E>
      Specified by:
      addLast in interface Deque<E>

    • 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>

    • 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

    • descendingIterator

      public Iterator<E> descendingIterator()
      Specified by:
      descendingIterator in interface Deque<E>

    • drainTo

      public int drainTo(Collection<? super E> c)
      Drains the queue to the specified collection.
      Specified by:
      drainTo in interface BlockingQueue<E>
      Parameters:
      c - The collection to add the elements to
      Returns:
      number of elements added to the collection
      Throws:
      UnsupportedOperationException - if the add operation is not supported by the specified collection
      ClassCastException - if the class of the elements held by this collection prevents them from being added to the specified collection
      NullPointerException - if c is null
      IllegalArgumentException - if c is this instance

    • drainTo

      public int drainTo(Collection<? super E> collection, int maxElements)
      Drains no more than the specified number of elements from the queue to the specified collection.
      Specified by:
      drainTo in interface BlockingQueue<E>
      Parameters:
      collection - collection to add the elements to
      maxElements - maximum number of elements to remove from the queue
      Returns:
      number of elements added to the collection
      Throws:
      UnsupportedOperationException - if the add operation is not supported by the specified collection
      ClassCastException - if the class of the elements held by this collection prevents them from being added to the specified collection
      NullPointerException - if c is null
      IllegalArgumentException - if c is this instance

    • 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

    • getFirst

      public E getFirst()
      Specified by:
      getFirst in interface Deque<E>

    • getLast

      public E getLast()
      Specified by:
      getLast in interface Deque<E>

    • getTakeQueueLength

      int getTakeQueueLength()
      Gets the length of the queue of threads waiting to take instances from this deque. See disclaimer on accuracy in ReentrantLock.getWaitQueueLength(Condition).
      Returns:
      number of threads waiting on this deque's notEmpty condition.

    • hasTakeWaiters

      boolean hasTakeWaiters()
      Returns true if there are threads waiting to take instances from this deque. See disclaimer on accuracy in ReentrantLock.hasWaiters(Condition).
      Returns:
      true if there is at least one thread waiting on this deque's notEmpty condition.

    • interruptTakeWaiters

      void interruptTakeWaiters()
      Interrupts the threads currently waiting to take an object from the pool. See disclaimer on accuracy in ReentrantLock.getWaitingThreads(Condition).

    • 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 a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.
      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

    • linkFirst

      private boolean linkFirst(E e)
      Links provided element as first element, or returns false if full.
      Parameters:
      e - The element to link as the first element.
      Returns:
      true if successful, otherwise false

    • linkLast

      private boolean linkLast(E e)
      Links provided element as last element, or returns false if full.
      Parameters:
      e - The element to link as the last element.
      Returns:
      true if successful, otherwise false

    • offer

      public boolean offer(E e)
      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>

    • offer

      boolean offer(E e, Duration timeout) throws InterruptedException
      Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.

      This method is equivalent to offerLast(Object, long, TimeUnit)

      Parameters:
      e - element to link
      timeout - length of time to wait
      Returns:
      true if successful, otherwise false
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • offer

      public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException
      Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.

      This method is equivalent to offerLast(Object, long, TimeUnit)

      Specified by:
      offer in interface BlockingDeque<E>
      Specified by:
      offer in interface BlockingQueue<E>
      Parameters:
      e - element to link
      timeout - length of time to wait
      unit - units that timeout is expressed in
      Returns:
      true if successful, otherwise false
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • offerFirst

      public boolean offerFirst(E e)
      Specified by:
      offerFirst in interface BlockingDeque<E>
      Specified by:
      offerFirst in interface Deque<E>

    • offerFirst

      boolean offerFirst(E e, Duration timeout) throws InterruptedException
      Links the provided element as the first in the queue, waiting up to the specified time to do so if the queue is full.
      Parameters:
      e - element to link
      timeout - length of time to wait
      Returns:
      true if successful, otherwise false
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • offerFirst

      public boolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException
      Links the provided element as the first in the queue, waiting up to the specified time to do so if the queue is full.
      Specified by:
      offerFirst in interface BlockingDeque<E>
      Parameters:
      e - element to link
      timeout - length of time to wait
      unit - units that timeout is expressed in
      Returns:
      true if successful, otherwise false
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • offerLast

      public boolean offerLast(E e)
      Specified by:
      offerLast in interface BlockingDeque<E>
      Specified by:
      offerLast in interface Deque<E>

    • offerLast

      boolean offerLast(E e, Duration timeout) throws InterruptedException
      Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.
      Parameters:
      e - element to link
      timeout - length of time to wait
      Returns:
      true if successful, otherwise false
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whist waiting for space

    • offerLast

      public boolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException
      Links the provided element as the last in the queue, waiting up to the specified time to do so if the queue is full.
      Specified by:
      offerLast in interface BlockingDeque<E>
      Parameters:
      e - element to link
      timeout - length of time to wait
      unit - units that timeout is expressed in
      Returns:
      true if successful, otherwise false
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whist waiting for space

    • peek

      public E peek()
      Specified by:
      peek in interface BlockingDeque<E>
      Specified by:
      peek in interface Deque<E>
      Specified by:
      peek in interface Queue<E>

    • peekFirst

      public E peekFirst()
      Specified by:
      peekFirst in interface Deque<E>

    • peekLast

      public E peekLast()
      Specified by:
      peekLast in interface Deque<E>

    • poll

      public E poll()
      Specified by:
      poll in interface BlockingDeque<E>
      Specified by:
      poll in interface Deque<E>
      Specified by:
      poll in interface Queue<E>

    • poll

      E poll(Duration timeout) throws InterruptedException
      Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.

      This method is equivalent to pollFirst(long, TimeUnit).

      Parameters:
      timeout - length of time to wait
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • poll

      public E poll(long timeout, TimeUnit unit) throws InterruptedException
      Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.

      This method is equivalent to pollFirst(long, TimeUnit).

      Specified by:
      poll in interface BlockingDeque<E>
      Specified by:
      poll in interface BlockingQueue<E>
      Parameters:
      timeout - length of time to wait
      unit - units that timeout is expressed in
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • pollFirst

      public E pollFirst()
      Specified by:
      pollFirst in interface Deque<E>

    • pollFirst

      E pollFirst(Duration timeout) throws InterruptedException
      Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.
      Parameters:
      timeout - length of time to wait
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • pollFirst

      public E pollFirst(long timeout, TimeUnit unit) throws InterruptedException
      Unlinks the first element in the queue, waiting up to the specified time to do so if the queue is empty.
      Specified by:
      pollFirst in interface BlockingDeque<E>
      Parameters:
      timeout - length of time to wait
      unit - units that timeout is expressed in
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • pollLast

      public E pollLast()
      Specified by:
      pollLast in interface Deque<E>

    • pollLast

      E pollLast(Duration timeout) throws InterruptedException
      Unlinks the last element in the queue, waiting up to the specified time to do so if the queue is empty.
      Parameters:
      timeout - length of time to wait
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • pollLast

      public E pollLast(long timeout, TimeUnit unit) throws InterruptedException
      Unlinks the last element in the queue, waiting up to the specified time to do so if the queue is empty.
      Specified by:
      pollLast in interface BlockingDeque<E>
      Parameters:
      timeout - length of time to wait
      unit - units that timeout is expressed in
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • pop

      public E pop()
      Specified by:
      pop in interface Deque<E>

    • push

      public void push(E e)
      Specified by:
      push in interface BlockingDeque<E>
      Specified by:
      push in interface Deque<E>

    • put

      public void put(E e) throws InterruptedException
      Links the provided element as the last in the queue, waiting until there is space to do so if the queue is full.

      This method is equivalent to putLast(Object).

      Specified by:
      put in interface BlockingDeque<E>
      Specified by:
      put in interface BlockingQueue<E>
      Parameters:
      e - element to link
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • putFirst

      public void putFirst(E e) throws InterruptedException
      Links the provided element as the first in the queue, waiting until there is space to do so if the queue is full.
      Specified by:
      putFirst in interface BlockingDeque<E>
      Parameters:
      e - element to link
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • putLast

      public void putLast(E e) throws InterruptedException
      Links the provided element as the last in the queue, waiting until there is space to do so if the queue is full.
      Specified by:
      putLast in interface BlockingDeque<E>
      Parameters:
      e - element to link
      Throws:
      NullPointerException - if e is null
      InterruptedException - if the thread is interrupted whilst waiting for space

    • readObject

      private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException
      Reconstitutes this deque from a stream (that is, deserialize it).
      Parameters:
      s - the stream
      Throws:
      IOException
      ClassNotFoundException

    • 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 number of additional elements the queue is able to accept

    • 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

    • 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

    • removeFirst

      public E removeFirst()
      Specified by:
      removeFirst in interface Deque<E>

    • removeFirstOccurrence

      public boolean removeFirstOccurrence(Object o)
      Specified by:
      removeFirstOccurrence in interface BlockingDeque<E>
      Specified by:
      removeFirstOccurrence in interface Deque<E>

    • removeLast

      public E removeLast()
      Specified by:
      removeLast in interface Deque<E>

    • removeLastOccurrence

      public boolean removeLastOccurrence(Object o)
      Specified by:
      removeLastOccurrence in interface BlockingDeque<E>
      Specified by:
      removeLastOccurrence in interface Deque<E>

    • 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>
      Specified by:
      size in class AbstractCollection<E>
      Returns:
      the number of elements in this deque

    • take

      public E take() throws InterruptedException
      Unlinks the first element in the queue, waiting until there is an element to unlink if the queue is empty.

      This method is equivalent to takeFirst().

      Specified by:
      take in interface BlockingDeque<E>
      Specified by:
      take in interface BlockingQueue<E>
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • takeFirst

      public E takeFirst() throws InterruptedException
      Unlinks the first element in the queue, waiting until there is an element to unlink if the queue is empty.
      Specified by:
      takeFirst in interface BlockingDeque<E>
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • takeLast

      public E takeLast() throws InterruptedException
      Unlinks the last element in the queue, waiting until there is an element to unlink if the queue is empty.
      Specified by:
      takeLast in interface BlockingDeque<E>
      Returns:
      the unlinked element
      Throws:
      InterruptedException - if the current thread is interrupted

    • 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)
      Specified by:
      toArray in interface Collection<E>
      Overrides:
      toArray in class AbstractCollection<E>

    • toString

      public String toString()
      Overrides:
      toString in class AbstractCollection<E>

    • unlink

      private void unlink(LinkedBlockingDeque.Node<E> x)
      Unlinks the provided node.
      Parameters:
      x - The node to unlink

    • unlinkFirst

      private E unlinkFirst()
      Removes and returns the first element, or null if empty.
      Returns:
      The first element or null if empty

    • unlinkLast

      private E unlinkLast()
      Removes and returns the last element, or null if empty.
      Returns:
      The first element or null if empty

    • writeObject

      private void writeObject(ObjectOutputStream s) throws IOException
      Saves the state of this deque to a stream (that is, serialize it).
      Parameters:
      s - the stream
      Throws:
      IOException - if I/O errors occur while writing to the underlying OutputStream