E
- the type of elements held in this collectionpublic interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E>
Deque
that additionally supports blocking operations that wait
for the deque to become non-empty when retrieving an element, and wait for
space to become available in the deque when storing an element.
BlockingDeque methods come in four forms, with different ways of handling operations that cannot be satisfied immediately, but may be satisfied at some point in the future: one throws an exception, the second returns a special value (either null or false, depending on the operation), the third blocks the current thread indefinitely until the operation can succeed, and the fourth blocks for only a given maximum time limit before giving up. These methods are summarized in the following table:
First Element (Head) | ||||
Throws exception | Special value | Blocks | Times out | |
Insert | addFirst(e) |
offerFirst(e) |
putFirst(e) |
offerFirst(e, time, unit) |
Remove | removeFirst() |
pollFirst() |
takeFirst() |
pollFirst(time, unit) |
Examine | getFirst() |
peekFirst() |
not applicable | not applicable |
Last Element (Tail) | ||||
Throws exception | Special value | Blocks | Times out | |
Insert | addLast(e) |
offerLast(e) |
putLast(e) |
offerLast(e, time, unit) |
Remove | removeLast() |
pollLast() |
takeLast() |
pollLast(time, unit) |
Examine | getLast() |
peekLast() |
not applicable | not applicable |
Like any BlockingQueue
, a BlockingDeque is thread safe,
does not permit null elements, and may (or may not) be
capacity-constrained.
A BlockingDeque implementation may be used directly as a FIFO BlockingQueue. The methods inherited from the BlockingQueue interface are precisely equivalent to BlockingDeque methods as indicated in the following table:
BlockingQueue Method | Equivalent BlockingDeque Method |
Insert | |
add(e) |
addLast(e) |
offer(e) |
offerLast(e) |
put(e) |
putLast(e) |
offer(e, time, unit) |
offerLast(e, time, unit) |
Remove | |
remove() |
removeFirst() |
poll() |
pollFirst() |
take() |
takeFirst() |
poll(time, unit) |
pollFirst(time, unit) |
Examine | |
element() |
getFirst() |
peek() |
peekFirst() |
Memory consistency effects: As with other concurrent
collections, actions in a thread prior to placing an object into a
BlockingDeque
happen-before
actions subsequent to the access or removal of that element from
the BlockingDeque
in another thread.
This interface is a member of the Java Collections Framework.
Modifier and Type | Method and Description |
---|---|
boolean |
add(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 throwing an
IllegalStateException if no space is currently available.
|
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.
|
boolean |
contains(Object o)
Returns true if this deque contains the specified element.
|
E |
element()
Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first 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 |
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(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(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.
|
void |
push(E e)
Pushes an element onto the stack represented by this deque.
|
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.
|
E |
remove()
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
|
boolean |
remove(Object o)
Removes the first occurrence of the specified element from this deque.
|
boolean |
removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element from this deque.
|
boolean |
removeLastOccurrence(Object o)
Removes the last occurrence of the specified element from this deque.
|
int |
size()
Returns the number of 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.
|
drainTo, drainTo, remainingCapacity
descendingIterator, getFirst, getLast, peekFirst, peekLast, pollFirst, pollLast, pop, removeFirst, removeLast
void addFirst(E e)
offerFirst
.addFirst
in interface Deque<E>
e
- the element to addIllegalStateException
- if the element cannot be added at this
time due to capacity restrictionsClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequevoid addLast(E e)
offerLast
.addLast
in interface Deque<E>
e
- the element to addIllegalStateException
- if the element cannot be added at this
time due to capacity restrictionsClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeboolean offerFirst(E e)
addFirst
method, which can
fail to insert an element only by throwing an exception.offerFirst
in interface Deque<E>
e
- the element to addClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeboolean offerLast(E e)
addLast
method, which can
fail to insert an element only by throwing an exception.offerLast
in interface Deque<E>
e
- the element to addClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequevoid putFirst(E e) throws InterruptedException
e
- the element to addInterruptedException
- if interrupted while waitingClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequevoid putLast(E e) throws InterruptedException
e
- the element to addInterruptedException
- if interrupted while waitingClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeboolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException
e
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterInterruptedException
- if interrupted while waitingClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeboolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException
e
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterInterruptedException
- if interrupted while waitingClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeE takeFirst() throws InterruptedException
InterruptedException
- if interrupted while waitingE takeLast() throws InterruptedException
InterruptedException
- if interrupted while waitingE pollFirst(long timeout, TimeUnit unit) throws InterruptedException
timeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterInterruptedException
- if interrupted while waitingE pollLast(long timeout, TimeUnit unit) throws InterruptedException
timeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterInterruptedException
- if interrupted while waitingboolean removeFirstOccurrence(Object o)
removeFirstOccurrence
in interface Deque<E>
o
- element to be removed from this deque, if presentClassCastException
- if the class of the specified element
is incompatible with this deque
(optional)NullPointerException
- if the specified element is null
(optional)boolean removeLastOccurrence(Object o)
removeLastOccurrence
in interface Deque<E>
o
- element to be removed from this deque, if presentClassCastException
- if the class of the specified element
is incompatible with this deque
(optional)NullPointerException
- if the specified element is null
(optional)boolean add(E e)
offer
.
This method is equivalent to addLast
.
add
in interface BlockingQueue<E>
add
in interface Collection<E>
add
in interface Deque<E>
add
in interface Queue<E>
e
- the element to addCollection.add(E)
)IllegalStateException
- if the element cannot be added at this
time due to capacity restrictionsClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeboolean offer(E e)
add(E)
method, which can fail to
insert an element only by throwing an exception.
This method is equivalent to offerLast
.
offer
in interface BlockingQueue<E>
offer
in interface Deque<E>
offer
in interface Queue<E>
e
- the element to addClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequevoid put(E e) throws InterruptedException
This method is equivalent to putLast
.
put
in interface BlockingQueue<E>
e
- the element to addInterruptedException
- if interrupted while waitingClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeboolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException
This method is equivalent to
offerLast
.
offer
in interface BlockingQueue<E>
e
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterInterruptedException
- if interrupted while waitingClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this dequeE remove()
poll
only in that it
throws an exception if this deque is empty.
This method is equivalent to removeFirst
.
E poll()
This method is equivalent to Deque.pollFirst()
.
E take() throws InterruptedException
This method is equivalent to takeFirst
.
take
in interface BlockingQueue<E>
InterruptedException
- if interrupted while waitingE poll(long timeout, TimeUnit unit) throws InterruptedException
This method is equivalent to
pollFirst
.
poll
in interface BlockingQueue<E>
timeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterInterruptedException
- if interrupted while waitingE element()
E peek()
This method is equivalent to peekFirst
.
boolean remove(Object o)
This method is equivalent to
removeFirstOccurrence
.
remove
in interface BlockingQueue<E>
remove
in interface Collection<E>
remove
in interface Deque<E>
o
- element to be removed from this deque, if presentClassCastException
- if the class of the specified element
is incompatible with this deque
(optional)NullPointerException
- if the specified element is null
(optional)boolean contains(Object o)
contains
in interface BlockingQueue<E>
contains
in interface Collection<E>
contains
in interface Deque<E>
o
- object to be checked for containment in this dequeClassCastException
- if the class of the specified element
is incompatible with this deque
(optional)NullPointerException
- if the specified element is null
(optional)int size()
Iterator<E> iterator()
void push(E e)
This method is equivalent to addFirst
.
push
in interface Deque<E>
e
- the element to pushIllegalStateException
- if the element cannot be added at this
time due to capacity restrictionsClassCastException
- if the class of the specified element
prevents it from being added to this dequeNullPointerException
- if the specified element is nullIllegalArgumentException
- if some property of the specified
element prevents it from being added to this deque Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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