Interface BlockingDeque<E>
- Type Parameters:
E- the type of elements held in this deque
- All Superinterfaces:
BlockingQueue<E>,Collection<E>,Deque<E>,Iterable<E>,Queue<E>,SequencedCollection<E>
- All Known Implementing Classes:
LinkedBlockingDeque
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.
- Since:
- 1.6
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Method Summary
Modifier and TypeMethodDescriptionbooleanInserts 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, returningtrueupon success and throwing anIllegalStateExceptionif no space is currently available.voidInserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing anIllegalStateExceptionif no space is currently available.voidInserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing anIllegalStateExceptionif no space is currently available.booleanReturnstrueif this deque contains the specified element.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()Returns an iterator over the elements in this deque in proper sequence.booleanInserts 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, returningtrueupon success andfalseif no space is currently available.booleanInserts 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.booleanofferFirst(E e) Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, returningtrueupon success andfalseif no space is currently available.booleanofferFirst(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.booleanInserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, returningtrueupon success andfalseif no space is currently available.booleanInserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.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 returnsnullif this deque is empty.poll()Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returnsnullif this deque is empty.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.Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.voidPushes 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 anIllegalStateExceptionif no space is currently available.voidInserts 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.voidInserts the specified element at the front of this deque, waiting if necessary for space to become available.voidInserts the specified element at the end of this deque, waiting if necessary for space to become available.remove()Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque).booleanRemoves the first occurrence of the specified element from this deque.booleanRemoves the first occurrence of the specified element from this deque.booleanRemoves the last occurrence of the specified element from this deque.intsize()Returns the number of elements in this deque.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.Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.takeLast()Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.Methods declared in interface java.util.concurrent.BlockingQueue
drainTo, drainTo, remainingCapacityMethods declared in interface java.util.Collection
clear, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArrayMethods declared in interface java.util.Deque
addAll, descendingIterator, getFirst, getLast, peekFirst, peekLast, pollFirst, pollLast, pop, removeFirst, removeLast, reversed
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Method Details
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addFirst
Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing anIllegalStateExceptionif no space is currently available. When using a capacity-restricted deque, it is generally preferable to useofferFirst.- Specified by:
addFirstin interfaceDeque<E>- Specified by:
addFirstin interfaceSequencedCollection<E>- Parameters:
e- the element to add- Throws:
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 deque
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addLast
Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing anIllegalStateExceptionif no space is currently available. When using a capacity-restricted deque, it is generally preferable to useofferLast.- Specified by:
addLastin interfaceDeque<E>- Specified by:
addLastin interfaceSequencedCollection<E>- Parameters:
e- the element to add- Throws:
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 deque
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offerFirst
Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, returningtrueupon success andfalseif no space is currently available. When using a capacity-restricted deque, this method is generally preferable to theaddFirstmethod, which can fail to insert an element only by throwing an exception.- Specified by:
offerFirstin interfaceDeque<E>- Parameters:
e- the element to add- Returns:
trueif the element was added to this deque, elsefalse- Throws:
ClassCastException- 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
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offerLast
Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, returningtrueupon success andfalseif no space is currently available. When using a capacity-restricted deque, this method is generally preferable to theaddLastmethod, which can fail to insert an element only by throwing an exception.- Specified by:
offerLastin interfaceDeque<E>- Parameters:
e- the element to add- Returns:
trueif the element was added to this deque, elsefalse- Throws:
ClassCastException- 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
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putFirst
Inserts the specified element at the front of this deque, waiting if necessary for space to become available.- Parameters:
e- the element to add- Throws:
InterruptedException- 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 deque
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putLast
Inserts the specified element at the end of this deque, waiting if necessary for space to become available.- Parameters:
e- the element to add- Throws:
InterruptedException- 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 deque
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offerFirst
Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.- Parameters:
e- the element to addtimeout- how long to wait before giving up, in units ofunitunit- aTimeUnitdetermining how to interpret thetimeoutparameter- Returns:
trueif successful, orfalseif the specified waiting time elapses before space is available- Throws:
InterruptedException- 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 deque
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offerLast
Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.- Parameters:
e- the element to addtimeout- how long to wait before giving up, in units ofunitunit- aTimeUnitdetermining how to interpret thetimeoutparameter- Returns:
trueif successful, orfalseif the specified waiting time elapses before space is available- Throws:
InterruptedException- 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 deque
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takeFirst
Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.- Returns:
- the head of this deque
- Throws:
InterruptedException- if interrupted while waiting
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takeLast
Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.- Returns:
- the tail of this deque
- Throws:
InterruptedException- if interrupted while waiting
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pollFirst
Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.- Parameters:
timeout- how long to wait before giving up, in units ofunitunit- aTimeUnitdetermining how to interpret thetimeoutparameter- Returns:
- the head of this deque, or
nullif the specified waiting time elapses before an element is available - Throws:
InterruptedException- if interrupted while waiting
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pollLast
Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.- Parameters:
timeout- how long to wait before giving up, in units ofunitunit- aTimeUnitdetermining how to interpret thetimeoutparameter- Returns:
- the tail of this deque, or
nullif the specified waiting time elapses before an element is available - Throws:
InterruptedException- if interrupted while waiting
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removeFirstOccurrence
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 elementesuch thato.equals(e)(if such an element exists). Returnstrueif this deque contained the specified element (or equivalently, if this deque changed as a result of the call).- Specified by:
removeFirstOccurrencein interfaceDeque<E>- Parameters:
o- element to be removed from this deque, if present- Returns:
trueif an element was removed as a result of this call- Throws:
ClassCastException- if the class of the specified element is incompatible with this deque (optional)NullPointerException- if the specified element is null (optional)
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removeLastOccurrence
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 elementesuch thato.equals(e)(if such an element exists). Returnstrueif this deque contained the specified element (or equivalently, if this deque changed as a result of the call).- Specified by:
removeLastOccurrencein interfaceDeque<E>- Parameters:
o- element to be removed from this deque, if present- Returns:
trueif an element was removed as a result of this call- Throws:
ClassCastException- if the class of the specified element is incompatible with this deque (optional)NullPointerException- if the specified element is null (optional)
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add
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, returningtrueupon success and throwing anIllegalStateExceptionif no space is currently available. When using a capacity-restricted deque, it is generally preferable to useoffer.This method is equivalent to
addLast.- Specified by:
addin interfaceBlockingQueue<E>- Specified by:
addin interfaceCollection<E>- Specified by:
addin interfaceDeque<E>- Specified by:
addin interfaceQueue<E>- Parameters:
e- the element to add- Returns:
true(as specified byCollection.add(E))- Throws:
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 deque
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offer
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, returningtrueupon success andfalseif no space is currently available. When using a capacity-restricted deque, this method is generally preferable to theadd(E)method, which can fail to insert an element only by throwing an exception.This method is equivalent to
offerLast.- Specified by:
offerin interfaceBlockingQueue<E>- Specified by:
offerin interfaceDeque<E>- Specified by:
offerin interfaceQueue<E>- Parameters:
e- the element to add- Returns:
trueif the element was added to this queue, elsefalse- Throws:
ClassCastException- 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
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put
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:
putin interfaceBlockingQueue<E>- Parameters:
e- the element to add- Throws:
InterruptedException- 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 deque
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offer
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:
offerin interfaceBlockingQueue<E>- Parameters:
e- the element to addtimeout- how long to wait before giving up, in units ofunitunit- aTimeUnitdetermining how to interpret thetimeoutparameter- Returns:
trueif the element was added to this deque, elsefalse- Throws:
InterruptedException- 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 deque
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remove
E remove()Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque). This method differs frompoll()only in that it throws an exception if this deque is empty.This method is equivalent to
removeFirst. -
poll
E poll()Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returnsnullif this deque is empty.This method is equivalent to
Deque.pollFirst(). -
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.This method is equivalent to
takeFirst.- Specified by:
takein interfaceBlockingQueue<E>- Returns:
- the head of this deque
- Throws:
InterruptedException- if interrupted while waiting
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poll
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:
pollin interfaceBlockingQueue<E>- Parameters:
timeout- how long to wait before giving up, in units ofunitunit- aTimeUnitdetermining how to interpret thetimeoutparameter- Returns:
- the head of this deque, or
nullif the specified waiting time elapses before an element is available - Throws:
InterruptedException- if interrupted while waiting
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element
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peek
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remove
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 elementesuch thato.equals(e)(if such an element exists). Returnstrueif 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:
removein interfaceBlockingQueue<E>- Specified by:
removein interfaceCollection<E>- Specified by:
removein interfaceDeque<E>- Parameters:
o- element to be removed from this deque, if present- Returns:
trueif this deque changed as a result of the call- Throws:
ClassCastException- if the class of the specified element is incompatible with this deque (optional)NullPointerException- if the specified element is null (optional)
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contains
Returnstrueif this deque contains the specified element. More formally, returnstrueif and only if this deque contains at least one elementesuch thato.equals(e).- Specified by:
containsin interfaceBlockingQueue<E>- Specified by:
containsin interfaceCollection<E>- Specified by:
containsin interfaceDeque<E>- Parameters:
o- object to be checked for containment in this deque- Returns:
trueif this deque contains the specified element- Throws:
ClassCastException- if the class of the specified element is incompatible with this deque (optional)NullPointerException- if the specified element is null (optional)
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size
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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). -
push
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 anIllegalStateExceptionif no space is currently available.This method is equivalent to
addFirst.- Specified by:
pushin interfaceDeque<E>- Parameters:
e- the element to push- Throws:
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 deque
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