edu.emory.mathcs.backport.java.util.concurrent
Class LinkedBlockingDeque

java.lang.Object
  java.util.AbstractCollection
      edu.emory.mathcs.backport.java.util.AbstractCollection
          edu.emory.mathcs.backport.java.util.AbstractQueue
              edu.emory.mathcs.backport.java.util.concurrent.LinkedBlockingDeque

All Implemented Interfaces:

BlockingDeque, BlockingQueue, java.util.Collection, Deque, Queue, java.io.Serializable

public class LinkedBlockingDeque

extends AbstractQueue

implements BlockingDeque, java.io.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

Author:

Doug Lea

See Also:

Serialized Form

Constructor Summary

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

LinkedBlockingDeque(java.util.Collection 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.

LinkedBlockingDeque(int capacity)
Creates a LinkedBlockingDeque with the given (fixed) capacity.

Method Summary

boolean	add(java.lang.Object e) Inserts the specified element at the end of this deque unless it would violate capacity restrictions.
void	addFirst(java.lang.Object 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(java.lang.Object 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(java.lang.Object o) Returns true if this deque contains the specified element.
java.util.Iterator	descendingIterator() Returns an iterator over the elements in this deque in reverse sequential order.
int	drainTo(java.util.Collection c) Removes all available elements from this queue and adds them to the given collection.
int	drainTo(java.util.Collection c, int maxElements) Removes at most the given number of available elements from this queue and adds them to the given collection.
java.lang.Object	element() Retrieves, but does not remove, the head of the queue represented by this deque.
java.lang.Object	getFirst() Retrieves, but does not remove, the first element of this deque.
java.lang.Object	getLast() Retrieves, but does not remove, the last element of this deque.
java.util.Iterator	iterator() Returns an iterator over the elements in this deque in proper sequence.
boolean	offer(java.lang.Object 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(java.lang.Object 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(java.lang.Object 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(java.lang.Object 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(java.lang.Object 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(java.lang.Object 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.
java.lang.Object	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.
java.lang.Object	peekFirst() Retrieves, but does not remove, the first element of this deque, or returns null if this deque is empty.
java.lang.Object	peekLast() Retrieves, but does not remove, the last element of this deque, or returns null if this deque is empty.
java.lang.Object	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.
java.lang.Object	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.
java.lang.Object	pollFirst() Retrieves and removes the first element of this deque, or returns null if this deque is empty.
java.lang.Object	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.
java.lang.Object	pollLast() Retrieves and removes the last element of this deque, or returns null if this deque is empty.
java.lang.Object	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.
java.lang.Object	pop() Pops an element from the stack represented by this deque.
void	push(java.lang.Object e) Pushes an element onto the stack represented by this deque.
void	put(java.lang.Object 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(java.lang.Object e) Inserts the specified element at the front of this deque, waiting if necessary for space to become available.
void	putLast(java.lang.Object 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.
java.lang.Object	remove() Retrieves and removes the head of the queue represented by this deque.
boolean	remove(java.lang.Object o) Removes the first occurrence of the specified element from this deque.
java.lang.Object	removeFirst() Retrieves and removes the first element of this deque.
boolean	removeFirstOccurrence(java.lang.Object o) Removes the first occurrence of the specified element from this deque.
java.lang.Object	removeLast() Retrieves and removes the last element of this deque.
boolean	removeLastOccurrence(java.lang.Object o) Removes the last occurrence of the specified element from this deque.
int	size() Returns the number of elements in this deque.
java.lang.Object	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.
java.lang.Object	takeFirst() Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.
java.lang.Object	takeLast() Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.
java.lang.Object[]	toArray() Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).
java.lang.Object[]	toArray(java.lang.Object[] 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.
java.lang.String	toString()

Methods inherited from class edu.emory.mathcs.backport.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, removeAll, retainAll

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:

java.lang.IllegalArgumentException - if capacity is less than 1

LinkedBlockingDeque

public LinkedBlockingDeque(java.util.Collection 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:

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

Method Detail

addFirst

public void addFirst(java.lang.Object 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

Parameters:

e - the element to add

Throws:

java.lang.IllegalStateException - if the element cannot be added at this time due to capacity restrictions

java.lang.NullPointerException - if the specified element is null

addLast

public void addLast(java.lang.Object 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

Parameters:

e - the element to add

Throws:

java.lang.IllegalStateException - if the element cannot be added at this time due to capacity restrictions

java.lang.NullPointerException - if the specified element is null

offerFirst

public boolean offerFirst(java.lang.Object 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

Parameters:

e - the element to add

Throws:

java.lang.NullPointerException - if the specified element is null

offerLast

public boolean offerLast(java.lang.Object 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

Parameters:

e - the element to add

Throws:

java.lang.NullPointerException - if the specified element is null

putFirst

public void putFirst(java.lang.Object e)
              throws java.lang.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

Parameters:

e - the element to add

Throws:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting

putLast

public void putLast(java.lang.Object e)
             throws java.lang.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

Parameters:

e - the element to add

Throws:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting

offerFirst

public boolean offerFirst(java.lang.Object e,
                          long timeout,
                          TimeUnit unit)
                   throws java.lang.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

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:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting

offerLast

public boolean offerLast(java.lang.Object e,
                         long timeout,
                         TimeUnit unit)
                  throws java.lang.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

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:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting

removeFirst

public java.lang.Object 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

Returns:

the head of this deque

Throws:

java.util.NoSuchElementException

removeLast

public java.lang.Object 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

Returns:

the tail of this deque

Throws:

java.util.NoSuchElementException

pollFirst

public java.lang.Object 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

Returns:

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

pollLast

public java.lang.Object 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

Returns:

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

takeFirst

public java.lang.Object takeFirst()
                           throws java.lang.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

Returns:

the head of this deque

Throws:

java.lang.InterruptedException - if interrupted while waiting

takeLast

public java.lang.Object takeLast()
                          throws java.lang.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

Returns:

the tail of this deque

Throws:

java.lang.InterruptedException - if interrupted while waiting

pollFirst

public java.lang.Object pollFirst(long timeout,
                                  TimeUnit unit)
                           throws java.lang.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

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:

java.lang.InterruptedException - if interrupted while waiting

pollLast

public java.lang.Object pollLast(long timeout,
                                 TimeUnit unit)
                          throws java.lang.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

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:

java.lang.InterruptedException - if interrupted while waiting

getFirst

public java.lang.Object 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

Returns:

the head of this deque

Throws:

java.util.NoSuchElementException

getLast

public java.lang.Object 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

Returns:

the tail of this deque

Throws:

java.util.NoSuchElementException

peekFirst

public java.lang.Object 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

Returns:

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

peekLast

public java.lang.Object 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

Returns:

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

removeFirstOccurrence

public boolean removeFirstOccurrence(java.lang.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

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(java.lang.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

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(java.lang.Object 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(java.lang.Object).

Specified by:

add in interface BlockingDeque

Overrides:

add in class AbstractQueue

Parameters:

e - the element to add

Returns:

true (as specified by Collection.add(java.lang.Object))

Throws:

java.lang.IllegalStateException - if the element cannot be added at this time due to capacity restrictions

java.lang.NullPointerException - if the specified element is null

offer

public boolean offer(java.lang.Object 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(java.lang.Object) 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

Parameters:

e - the element to add

Throws:

java.lang.NullPointerException - if the specified element is null

put

public void put(java.lang.Object e)
         throws java.lang.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

Parameters:

e - the element to add

Throws:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting

offer

public boolean offer(java.lang.Object e,
                     long timeout,
                     TimeUnit unit)
              throws java.lang.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

Parameters:

e - the element to add

Returns:

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

Throws:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting

remove

public java.lang.Object 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

Overrides:

remove in class AbstractQueue

Returns:

the head of the queue represented by this deque

Throws:

java.util.NoSuchElementException - if this deque is empty

poll

public java.lang.Object 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

Returns:

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

take

public java.lang.Object take()
                      throws java.lang.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

Returns:

the head of this deque

Throws:

java.lang.InterruptedException - if interrupted while waiting

poll

public java.lang.Object poll(long timeout,
                             TimeUnit unit)
                      throws java.lang.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

Returns:

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

Throws:

java.lang.InterruptedException - if interrupted while waiting

element

public java.lang.Object 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

Overrides:

element in class AbstractQueue

Returns:

the head of the queue represented by this deque

Throws:

java.util.NoSuchElementException - if this deque is empty

peek

public java.lang.Object 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

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

Returns:

the remaining capacity

drainTo

public int drainTo(java.util.Collection 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

Parameters:

c - the collection to transfer elements into

Returns:

the number of elements transferred

Throws:

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

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

java.lang.NullPointerException - if the specified collection is null

java.lang.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(java.util.Collection 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

Parameters:

c - the collection to transfer elements into

maxElements - the maximum number of elements to transfer

Returns:

the number of elements transferred

Throws:

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

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

java.lang.NullPointerException - if the specified collection is null

java.lang.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(java.lang.Object e)

Description copied from interface: BlockingDeque

Pushes an element onto the stack represented by this deque. In other words, inserts the element at the front of this deque unless it would violate capacity restrictions.

This method is equivalent to addFirst.

Specified by:

push in interface BlockingDeque

Throws:

java.lang.IllegalStateException - if the element cannot be added at this time due to capacity restrictions

java.lang.NullPointerException - if the specified element is null

pop

public java.lang.Object 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

Returns:

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

Throws:

java.util.NoSuchElementException

remove

public boolean remove(java.lang.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

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

Returns:

the number of elements in this deque

contains

public boolean contains(java.lang.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

Parameters:

o - object to be checked for containment in this deque

Returns:

true if this deque contains the specified element

toArray

public java.lang.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 java.util.Collection

Overrides:

toArray in class AbstractCollection

Returns:

an array containing all of the elements in this deque

toArray

public java.lang.Object[] toArray(java.lang.Object[] 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 java.util.Collection

Overrides:

toArray in class AbstractCollection

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:

java.lang.ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque

java.lang.NullPointerException - if the specified array is null

toString

public java.lang.String toString()

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 java.util.Collection

Overrides:

clear in class AbstractQueue

iterator

public java.util.Iterator 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

Returns:

an iterator over the elements in this deque in proper sequence

descendingIterator

public java.util.Iterator 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 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:

descendingIterator in interface Deque

Returns:

an iterator over the elements in this deque in reverse sequence