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>
- All Known Implementing Classes:
LinkedBlockingDeque
public interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E>
A 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
Method Summary
Modifier and Type | Method | 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 |
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 |
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 |
boolean | contains(Object o) | Returns |
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 |
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 |
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 |
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 |
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 |
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 an |
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 declared in interface java.util.concurrent.BlockingQueue
drainTo, drainTo, remainingCapacity
Methods declared in interface java.util.Collection
clear, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArray
Methods declared in interface java.util.Deque
addAll, descendingIterator, getFirst, getLast, peekFirst, peekLast, pollFirst, pollLast, pop, removeFirst, removeLast
Methods declared in interface java.lang.Iterable
forEach
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 an IllegalStateException
if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offerFirst
.
- Specified by:
-
addFirst
in 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 an IllegalStateException
if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offerLast
.
- Specified by:
-
addLast
in 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, returning true
upon success and false
if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the addFirst
method, which can fail to insert an element only by throwing an exception.
- Specified by:
-
offerFirst
in 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, returning true
upon success and false
if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the addLast
method, which can fail to insert an element only by throwing an exception.
- Specified by:
-
offerLast
in 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 element e
such that o.equals(e)
(if such an element exists). Returns true
if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).
- Specified by:
-
removeFirstOccurrence
in 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 element e
such that o.equals(e)
(if such an element exists). Returns true
if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).
- Specified by:
-
removeLastOccurrence
in 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, returning true
upon success and throwing an IllegalStateException
if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offer
.
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, returning true
upon success and false
if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the add(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 from poll()
only in that it throws an exception if this deque is empty.
This method is equivalent to removeFirst
.
- Specified by:
-
remove
in interfaceDeque<E>
- Specified by:
-
remove
in interfaceQueue<E>
- Returns:
- the head of the queue represented by this deque
- Throws:
-
NoSuchElementException
- if this deque is empty
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 returns null
if this deque is empty.
This method is equivalent to Deque.pollFirst()
.
- Specified by:
-
poll
in interfaceDeque<E>
- Specified by:
-
poll
in interfaceQueue<E>
- Returns:
- the head of this deque, or
null
if this deque is empty
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()
Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque). This method differs from peek
only in that it throws an exception if this deque is empty.
This method is equivalent to getFirst
.
- Specified by:
-
element
in interfaceDeque<E>
- Specified by:
-
element
in interfaceQueue<E>
- Returns:
- the head of this deque
- Throws:
-
NoSuchElementException
- if this deque is empty
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 returns null
if this deque is empty.
This method is equivalent to peekFirst
.
- Specified by:
-
peek
in interfaceDeque<E>
- Specified by:
-
peek
in interfaceQueue<E>
- Returns:
- the head of this deque, or
null
if this deque is empty
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 element e
such that o.equals(e)
(if such an element exists). Returns true
if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).
This method is equivalent to removeFirstOccurrence
.
- Specified by:
-
remove
in 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)
Returns true
if this deque contains the specified element. More formally, returns true
if and only if this deque contains at least one element e
such that o.equals(e)
.
- Specified by:
-
contains
in 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.
- Specified by:
-
size
in interfaceCollection<E>
- Specified by:
-
size
in interfaceDeque<E>
- 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).
- Specified by:
-
iterator
in interfaceCollection<E>
- Specified by:
-
iterator
in interfaceDeque<E>
- Specified by:
-
iterator
in interfaceIterable<E>
- Returns:
- an iterator over the elements in this deque in proper sequence
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 an IllegalStateException
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