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- Type Parameters:
E- the type of elements held in this deque
- All Superinterfaces:
BlockingQueue<E>,Collection<E>,Deque<E>,Iterable<E>,Queue<E>
- All Known Implementing Classes:
LinkedBlockingDeque
public interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E>
ADequethat 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.BlockingDequemethods 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 (eithernullorfalse, 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:Summary of BlockingDeque methods 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, aBlockingDequeis thread safe, does not permit null elements, and may (or may not) be capacity-constrained.A
BlockingDequeimplementation may be used directly as a FIFOBlockingQueue. The methods inherited from theBlockingQueueinterface are precisely equivalent toBlockingDequemethods as indicated in the following table:Comparison of BlockingQueue and BlockingDeque methods BlockingQueueMethodEquivalent BlockingDequeMethodInsert 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
BlockingDequehappen-before actions subsequent to the access or removal of that element from theBlockingDequein another thread.This interface is a member of the Java Collections Framework.
- Since:
- 1.6
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description booleanadd(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, returningtrueupon success and throwing anIllegalStateExceptionif no space is currently available.voidaddFirst(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 anIllegalStateExceptionif no space is currently available.voidaddLast(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 anIllegalStateExceptionif no space is currently available.booleancontains(Object o)Returnstrueif this deque contains the specified element.Eelement()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.booleanoffer(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, returningtrueupon success andfalseif no space is currently available.booleanoffer(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.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.booleanofferLast(E e)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.booleanofferLast(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.Epeek()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.Epoll()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.Epoll(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.EpollFirst(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.EpollLast(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.voidpush(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 anIllegalStateExceptionif no space is currently available.voidput(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.voidputFirst(E e)Inserts the specified element at the front of this deque, waiting if necessary for space to become available.voidputLast(E e)Inserts the specified element at the end of this deque, waiting if necessary for space to become available.Eremove()Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque).booleanremove(Object o)Removes the first occurrence of the specified element from this deque.booleanremoveFirstOccurrence(Object o)Removes the first occurrence of the specified element from this deque.booleanremoveLastOccurrence(Object o)Removes the last occurrence of the specified element from this deque.intsize()Returns the number of elements in this deque.Etake()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.EtakeFirst()Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.EtakeLast()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, remainingCapacity
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Methods declared in interface java.util.Collection
clear, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArray
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Methods declared in interface java.util.Deque
addAll, descendingIterator, getFirst, getLast, peekFirst, peekLast, pollFirst, pollLast, pop, removeFirst, removeLast
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Method Detail
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addFirst
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 anIllegalStateExceptionif no space is currently available. When using a capacity-restricted deque, it is generally preferable to useofferFirst.- Specified by:
addFirstin interfaceDeque<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
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 anIllegalStateExceptionif no space is currently available. When using a capacity-restricted deque, it is generally preferable to useofferLast.- Specified by:
addLastin interfaceDeque<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
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, 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
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, 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
void putFirst(E e) throws InterruptedException
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
void putLast(E e) throws InterruptedException
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
boolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException
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
boolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException
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
E takeFirst() throws InterruptedException
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
E takeLast() throws InterruptedException
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
E pollFirst(long timeout, TimeUnit unit) throws InterruptedException
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
E pollLast(long timeout, TimeUnit unit) throws InterruptedException
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
boolean removeFirstOccurrence(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 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
boolean removeLastOccurrence(Object o)
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
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, 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
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, 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
void put(E e) throws InterruptedException
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
boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException
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.
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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().
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take
E take() throws InterruptedException
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
E poll(long timeout, TimeUnit unit) throws InterruptedException
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
E element()
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peek
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 returnsnullif this deque is empty.This method is equivalent to
peekFirst.
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remove
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 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
boolean contains(Object o)
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
int size()
Returns the number of elements in this deque.
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iterator
Iterator<E> iterator()
Returns an iterator over the elements in this deque in proper sequence. The elements will be returned in order from first (head) to last (tail).
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push
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 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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