Module java.base

Class LinkedBlockingDeque<E>

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      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)  
      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)  
      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)  
      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)  
      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.
      String toString​()  
    • Constructor Detail

      • 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 Detail

      • 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>
        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>
        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
      • 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>
        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>
        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
      • 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>
        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>
        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
      • 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
      • 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
      • 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>
        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>
      • 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