Interface BlockingDeque<E>
-
- Type Parameters:
-
E
- the type of elements held in this collection
- 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>
ADeque
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 (eithernull
orfalse
, 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
, aBlockingDeque
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 FIFOBlockingQueue
. The methods inherited from theBlockingQueue
interface are precisely equivalent toBlockingDeque
methods as indicated in the following table:Comparison of BlockingQueue and BlockingDeque methods BlockingQueue
MethodEquivalent BlockingDeque
MethodInsert 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 theBlockingDeque
in another thread.This interface is a member of the Java Collections Framework.
- Since:
- 1.6
-
-
Method Summary
All Methods Instance Methods Abstract Methods 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, returningtrue
upon success and throwing anIllegalStateException
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 anIllegalStateException
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 anIllegalStateException
if no space is currently available.boolean
contains(Object o)
Returnstrue
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, returningtrue
upon success andfalse
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, returningtrue
upon success andfalse
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, returningtrue
upon success andfalse
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 returnsnull
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 returnsnull
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 (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing anIllegalStateException
if no space is currently available.void
put(E e)
Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.void
putFirst(E e)
Inserts the specified element at the front of this deque, waiting if necessary for space to become available.void
putLast(E e)
Inserts the specified element at the end of this deque, waiting if necessary for space to become available.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.-
Methods inherited from interface java.util.concurrent.BlockingQueue
drainTo, drainTo, remainingCapacity
-
Methods inherited from interface java.util.Deque
descendingIterator, getFirst, getLast, peekFirst, peekLast, pollFirst, pollLast, pop, removeFirst, removeLast
-
Methods inherited from interface java.util.Collection
addAll, clear, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray
-
-
-
-
Method Detail
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 anIllegalStateException
if no space is currently available. When using a capacity-restricted deque, it is generally preferable to useofferFirst
.- Specified by:
-
addFirst
in interfaceDeque<E>
- Parameters:
-
e
- the element to add - Throws:
-
IllegalStateException
- if the element cannot be added at this time due to capacity restrictions -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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 anIllegalStateException
if no space is currently available. When using a capacity-restricted deque, it is generally preferable to useofferLast
.- Specified by:
-
addLast
in interfaceDeque<E>
- Parameters:
-
e
- the element to add - Throws:
-
IllegalStateException
- if the element cannot be added at this time due to capacity restrictions -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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, returningtrue
upon success andfalse
if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to theaddFirst
method, which can fail to insert an element only by throwing an exception.- Specified by:
-
offerFirst
in interfaceDeque<E>
- Parameters:
-
e
- the element to add - Returns:
-
true
if the element was added to this deque, elsefalse
- Throws:
-
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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, returningtrue
upon success andfalse
if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to theaddLast
method, which can fail to insert an element only by throwing an exception.- Specified by:
-
offerLast
in interfaceDeque<E>
- Parameters:
-
e
- the element to add - Returns:
-
true
if the element was added to this deque, elsefalse
- Throws:
-
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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 waiting -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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 waiting -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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 add -
timeout
- how long to wait before giving up, in units ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
true
if successful, orfalse
if the specified waiting time elapses before space is available - Throws:
-
InterruptedException
- if interrupted while waiting -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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 add -
timeout
- how long to wait before giving up, in units ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
true
if successful, orfalse
if the specified waiting time elapses before space is available - Throws:
-
InterruptedException
- if interrupted while waiting -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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
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
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 ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
the head of this deque, or
null
if the specified waiting time elapses before an element is available - Throws:
-
InterruptedException
- if interrupted while waiting
pollLast
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 ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
the tail of this deque, or
null
if the specified waiting time elapses before an element is available - Throws:
-
InterruptedException
- if interrupted while waiting
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 elemente
such thato.equals(e)
(if such an element exists). Returnstrue
if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).- Specified by:
-
removeFirstOccurrence
in interfaceDeque<E>
- Parameters:
-
o
- element to be removed from this deque, if present - Returns:
-
true
if an element was removed as a result of this call - Throws:
-
ClassCastException
- if the class of the specified element is incompatible with this deque (optional) -
NullPointerException
- if the specified element is null (optional)
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 elemente
such thato.equals(e)
(if such an element exists). Returnstrue
if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).- Specified by:
-
removeLastOccurrence
in interfaceDeque<E>
- Parameters:
-
o
- element to be removed from this deque, if present - Returns:
-
true
if an element was removed as a result of this call - Throws:
-
ClassCastException
- if the class of the specified element is incompatible with this deque (optional) -
NullPointerException
- if the specified element is null (optional)
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, returningtrue
upon success and throwing anIllegalStateException
if 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:
-
add
in interfaceBlockingQueue<E>
- Specified by:
-
add
in interfaceCollection<E>
- Specified by:
-
add
in interfaceDeque<E>
- Specified by:
-
add
in 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 restrictions -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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, returningtrue
upon success andfalse
if 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:
-
offer
in interfaceBlockingQueue<E>
- Specified by:
-
offer
in interfaceDeque<E>
- Specified by:
-
offer
in interfaceQueue<E>
- Parameters:
-
e
- the element to add - Returns:
-
true
if the element was added to this queue, elsefalse
- Throws:
-
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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:
-
put
in interfaceBlockingQueue<E>
- Parameters:
-
e
- the element to add - Throws:
-
InterruptedException
- if interrupted while waiting -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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:
-
offer
in interfaceBlockingQueue<E>
- Parameters:
-
e
- the element to add -
timeout
- how long to wait before giving up, in units ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
true
if the element was added to this deque, elsefalse
- Throws:
-
InterruptedException
- if interrupted while waiting -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
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 returnsnull
if this deque is empty.This method is equivalent to
Deque.pollFirst()
.
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:
-
take
in interfaceBlockingQueue<E>
- Returns:
- the head of this deque
- Throws:
-
InterruptedException
- if interrupted while waiting
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:
-
poll
in interfaceBlockingQueue<E>
- Parameters:
-
timeout
- how long to wait before giving up, in units ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
the head of this deque, or
null
if the specified waiting time elapses before an element is available - Throws:
-
InterruptedException
- if interrupted while waiting
element
E element()
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 returnsnull
if this deque is empty.This method is equivalent to
peekFirst
.
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 elemente
such thato.equals(e)
(if such an element exists). Returnstrue
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 interfaceBlockingQueue<E>
- Specified by:
-
remove
in interfaceCollection<E>
- Specified by:
-
remove
in interfaceDeque<E>
- Parameters:
-
o
- element to be removed from this deque, if present - Returns:
-
true
if 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)
contains
boolean contains(Object o)
Returnstrue
if this deque contains the specified element. More formally, returnstrue
if and only if this deque contains at least one elemente
such thato.equals(e)
.- Specified by:
-
contains
in interfaceBlockingQueue<E>
- Specified by:
-
contains
in interfaceCollection<E>
- Specified by:
-
contains
in interfaceDeque<E>
- Parameters:
-
o
- object to be checked for containment in this deque - Returns:
-
true
if 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)
size
int size()
Returns the number of elements in this deque.
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).
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 anIllegalStateException
if no space is currently available.This method is equivalent to
addFirst
.- Specified by:
-
push
in interfaceDeque<E>
- Parameters:
-
e
- the element to push - Throws:
-
IllegalStateException
- if the element cannot be added at this time due to capacity restrictions -
ClassCastException
- if the class of the specified element prevents it from being added to this deque -
NullPointerException
- if the specified element is null -
IllegalArgumentException
- if some property of the specified element prevents it from being added to this deque
-
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