BlockingDeque
public
interface
BlockingDeque
implements
BlockingQueue<E>,
Deque<E>
java.util.concurrent.BlockingDeque<E>
|
Known indirect subclasses
|
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:
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:
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.
Summary
Public methods |
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
boolean
|
contains(Object o)
Returns true if this deque contains the specified element.
|
abstract
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).
|
abstract
Iterator<E>
|
iterator()
Returns an iterator over the elements in this deque in proper sequence.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
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.
|
abstract
void
|
putFirst(E e)
Inserts the specified element at the front of this deque,
waiting if necessary for space to become available.
|
abstract
void
|
putLast(E e)
Inserts the specified element at the end of this deque,
waiting if necessary for space to become available.
|
abstract
E
|
remove()
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
|
abstract
boolean
|
remove(Object o)
Removes the first occurrence of the specified element from this deque.
|
abstract
boolean
|
removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element from this deque.
|
abstract
boolean
|
removeLastOccurrence(Object o)
Removes the last occurrence of the specified element from this deque.
|
abstract
int
|
size()
Returns the number of elements in this deque.
|
abstract
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.
|
abstract
E
|
takeFirst()
Retrieves and removes the first element of this deque, waiting
if necessary until an element becomes available.
|
abstract
E
|
takeLast()
Retrieves and removes the last element of this deque, waiting
if necessary until an element becomes available.
|
Inherited methods |
From interface
java.util.concurrent.BlockingQueue
abstract
boolean
|
add(E e)
Inserts the specified element into this queue 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.
|
abstract
boolean
|
contains(Object o)
Returns true if this queue contains the specified element.
|
abstract
int
|
drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them
to the given collection.
|
abstract
int
|
drainTo(Collection<? super E> c, int maxElements)
Removes at most the given number of available elements from
this queue and adds them to the given collection.
|
abstract
boolean
|
offer(E e)
Inserts the specified element into this queue if it is possible to do
so immediately without violating capacity restrictions, returning
true upon success and false if no space is currently
available.
|
abstract
boolean
|
offer(E e, long timeout, TimeUnit unit)
Inserts the specified element into this queue, waiting up to the
specified wait time if necessary for space to become available.
|
abstract
E
|
poll(long timeout, TimeUnit unit)
Retrieves and removes the head of this queue, waiting up to the
specified wait time if necessary for an element to become available.
|
abstract
void
|
put(E e)
Inserts the specified element into this queue, waiting if necessary
for space to become available.
|
abstract
int
|
remainingCapacity()
Returns the number of additional elements that this queue can ideally
(in the absence of memory or resource constraints) accept without
blocking, or Integer.MAX_VALUE if there is no intrinsic
limit.
|
abstract
boolean
|
remove(Object o)
Removes a single instance of the specified element from this queue,
if it is present.
|
abstract
E
|
take()
Retrieves and removes the head of this queue, waiting if necessary
until an element becomes available.
|
|
From interface
java.util.Deque
abstract
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.
|
abstract
boolean
|
addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection at the end
of this deque, as if by calling addLast(E) on each one,
in the order that they are returned by the collection's iterator.
|
abstract
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.
|
abstract
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.
|
abstract
boolean
|
contains(Object o)
Returns true if this deque contains the specified element.
|
abstract
Iterator<E>
|
descendingIterator()
Returns an iterator over the elements in this deque in reverse
sequential order.
|
abstract
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).
|
abstract
E
|
getFirst()
Retrieves, but does not remove, the first element of this deque.
|
abstract
E
|
getLast()
Retrieves, but does not remove, the last element of this deque.
|
abstract
Iterator<E>
|
iterator()
Returns an iterator over the elements in this deque in proper sequence.
|
abstract
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.
|
abstract
boolean
|
offerFirst(E e)
Inserts the specified element at the front of this deque unless it would
violate capacity restrictions.
|
abstract
boolean
|
offerLast(E e)
Inserts the specified element at the end of this deque unless it would
violate capacity restrictions.
|
abstract
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.
|
abstract
E
|
peekFirst()
Retrieves, but does not remove, the first element of this deque,
or returns null if this deque is empty.
|
abstract
E
|
peekLast()
Retrieves, but does not remove, the last element of this deque,
or returns null if this deque is empty.
|
abstract
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.
|
abstract
E
|
pollFirst()
Retrieves and removes the first element of this deque,
or returns null if this deque is empty.
|
abstract
E
|
pollLast()
Retrieves and removes the last element of this deque,
or returns null if this deque is empty.
|
abstract
E
|
pop()
Pops an element from the stack represented by this deque.
|
abstract
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.
|
abstract
E
|
remove()
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
|
abstract
boolean
|
remove(Object o)
Removes the first occurrence of the specified element from this deque.
|
abstract
E
|
removeFirst()
Retrieves and removes the first element of this deque.
|
abstract
boolean
|
removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element from this deque.
|
abstract
E
|
removeLast()
Retrieves and removes the last element of this deque.
|
abstract
boolean
|
removeLastOccurrence(Object o)
Removes the last occurrence of the specified element from this deque.
|
default
Deque<E>
|
reversed()
Returns a reverse-ordered view of this collection.
|
abstract
int
|
size()
Returns the number of elements in this deque.
|
|
From interface
java.util.Queue
abstract
boolean
|
add(E e)
Inserts the specified element into this queue 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.
|
abstract
E
|
element()
Retrieves, but does not remove, the head of this queue.
|
abstract
boolean
|
offer(E e)
Inserts the specified element into this queue if it is possible to do
so immediately without violating capacity restrictions.
|
abstract
E
|
peek()
Retrieves, but does not remove, the head of this queue,
or returns null if this queue is empty.
|
abstract
E
|
poll()
Retrieves and removes the head of this queue,
or returns null if this queue is empty.
|
abstract
E
|
remove()
Retrieves and removes the head of this queue.
|
|
From interface
java.util.SequencedCollection
default
void
|
addFirst(E e)
Adds an element as the first element of this collection (optional operation).
|
default
void
|
addLast(E e)
Adds an element as the last element of this collection (optional operation).
|
default
E
|
getFirst()
Gets the first element of this collection.
|
default
E
|
getLast()
Gets the last element of this collection.
|
default
E
|
removeFirst()
Removes and returns the first element of this collection (optional operation).
|
default
E
|
removeLast()
Removes and returns the last element of this collection (optional operation).
|
abstract
SequencedCollection<E>
|
reversed()
Returns a reverse-ordered view of this collection.
|
|
From interface
java.util.Collection
abstract
boolean
|
add(E e)
Ensures that this collection contains the specified element (optional
operation).
|
abstract
boolean
|
addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this collection
(optional operation).
|
abstract
void
|
clear()
Removes all of the elements from this collection (optional operation).
|
abstract
boolean
|
contains(Object o)
Returns true if this collection contains the specified element.
|
abstract
boolean
|
containsAll(Collection<?> c)
Returns true if this collection contains all of the elements
in the specified collection.
|
abstract
boolean
|
equals(Object o)
Compares the specified object with this collection for equality.
|
abstract
int
|
hashCode()
Returns the hash code value for this collection.
|
abstract
boolean
|
isEmpty()
Returns true if this collection contains no elements.
|
abstract
Iterator<E>
|
iterator()
Returns an iterator over the elements in this collection.
|
default
Stream<E>
|
parallelStream()
Returns a possibly parallel Stream with this collection as its
source.
|
abstract
boolean
|
remove(Object o)
Removes a single instance of the specified element from this
collection, if it is present (optional operation).
|
abstract
boolean
|
removeAll(Collection<?> c)
Removes all of this collection's elements that are also contained in the
specified collection (optional operation).
|
default
boolean
|
removeIf(Predicate<? super E> filter)
Removes all of the elements of this collection that satisfy the given
predicate.
|
abstract
boolean
|
retainAll(Collection<?> c)
Retains only the elements in this collection that are contained in the
specified collection (optional operation).
|
abstract
int
|
size()
Returns the number of elements in this collection.
|
default
Spliterator<E>
|
spliterator()
Creates a Spliterator over the elements in this collection.
|
default
Stream<E>
|
stream()
Returns a sequential Stream with this collection as its source.
|
abstract
<T>
T[]
|
toArray(T[] a)
Returns an array containing all of the elements in this collection;
the runtime type of the returned array is that of the specified array.
|
abstract
Object[]
|
toArray()
Returns an array containing all of the elements in this collection.
|
default
<T>
T[]
|
toArray(IntFunction<T[]> generator)
Returns an array containing all of the elements in this collection,
using the provided generator function to allocate the returned array.
|
|
From interface
java.lang.Iterable
default
void
|
forEach(Consumer<? super T> action)
Performs the given action for each element of the Iterable
until all elements have been processed or the action throws an
exception.
|
abstract
Iterator<E>
|
iterator()
Returns an iterator over elements of type T .
|
default
Spliterator<E>
|
spliterator()
Creates a Spliterator over the elements described by this
Iterable .
|
|
Public methods
add
public abstract 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
.
Parameters |
e |
E : the element to add |
addFirst
public abstract 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
.
Parameters |
e |
E : the element to add |
addLast
public abstract 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
.
Parameters |
e |
E : the element to add |
contains
public abstract 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)
.
Parameters |
o |
Object : object to be checked for containment in this deque |
Returns |
boolean |
true if this deque contains the specified element |
element
public abstract 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
.
Returns |
E |
the head of this deque |
iterator
public abstract 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).
Returns |
Iterator<E> |
an iterator over the elements in this deque in proper sequence |
offer
public abstract 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.
This method is equivalent to
offerLast
.
Parameters |
e |
E : the element to add |
timeout |
long : how long to wait before giving up, in units of
unit |
unit |
TimeUnit : a TimeUnit determining how to interpret the
timeout parameter |
Returns |
boolean |
true if the element was added to this deque, else
false |
offer
public abstract 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
.
Parameters |
e |
E : the element to add |
Returns |
boolean |
true if the element was added to this deque, else
false |
offerFirst
public abstract 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.
Parameters |
e |
E : the element to add |
Returns |
boolean |
true if the element was added to this deque, else
false |
offerFirst
public abstract 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.
Parameters |
e |
E : the element to add |
timeout |
long : how long to wait before giving up, in units of
unit |
unit |
TimeUnit : a TimeUnit determining how to interpret the
timeout parameter |
Returns |
boolean |
true if successful, or false if
the specified waiting time elapses before space is available |
offerLast
public abstract 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.
Parameters |
e |
E : the element to add |
Returns |
boolean |
true if the element was added to this deque, else
false |
offerLast
public abstract 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.
Parameters |
e |
E : the element to add |
timeout |
long : how long to wait before giving up, in units of
unit |
unit |
TimeUnit : a TimeUnit determining how to interpret the
timeout parameter |
Returns |
boolean |
true if successful, or false if
the specified waiting time elapses before space is available |
peek
public abstract 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
.
Returns |
E |
the head of this deque, or null if this deque is empty |
poll
public abstract 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.
This method is equivalent to
pollFirst
.
Parameters |
timeout |
long : how long to wait before giving up, in units of
unit |
unit |
TimeUnit : a TimeUnit determining how to interpret the
timeout parameter |
Returns |
E |
the head of this deque, or null if the
specified waiting time elapses before an element is available |
poll
public abstract 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()
.
Returns |
E |
the head of this deque, or null if this deque is empty |
pollFirst
public abstract 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.
Parameters |
timeout |
long : how long to wait before giving up, in units of
unit |
unit |
TimeUnit : a TimeUnit determining how to interpret the
timeout parameter |
Returns |
E |
the head of this deque, or null if the specified
waiting time elapses before an element is available |
pollLast
public abstract 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.
Parameters |
timeout |
long : how long to wait before giving up, in units of
unit |
unit |
TimeUnit : a TimeUnit determining how to interpret the
timeout parameter |
Returns |
E |
the tail of this deque, or null if the specified
waiting time elapses before an element is available |
push
public abstract 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
.
Parameters |
e |
E : the element to push |
put
public abstract 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.
This method is equivalent to putLast
.
Parameters |
e |
E : the element to add |
putFirst
public abstract void putFirst (E e)
Inserts the specified element at the front of this deque,
waiting if necessary for space to become available.
Parameters |
e |
E : the element to add |
putLast
public abstract void putLast (E e)
Inserts the specified element at the end of this deque,
waiting if necessary for space to become available.
Parameters |
e |
E : the element to add |
remove
public abstract 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
.
Returns |
E |
the head of the queue represented by this deque |
remove
public abstract 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
.
Parameters |
o |
Object : element to be removed from this deque, if present |
Returns |
boolean |
true if this deque changed as a result of the call |
removeFirstOccurrence
public abstract 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).
Parameters |
o |
Object : element to be removed from this deque, if present |
Returns |
boolean |
true if an element was removed as a result of this call |
removeLastOccurrence
public abstract 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).
Parameters |
o |
Object : element to be removed from this deque, if present |
Returns |
boolean |
true if an element was removed as a result of this call |
size
public abstract int size ()
Returns the number of elements in this deque.
Returns |
int |
the number of elements in this deque |
take
public abstract 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.
This method is equivalent to takeFirst
.
Returns |
E |
the head of this deque |
takeFirst
public abstract E takeFirst ()
Retrieves and removes the first element of this deque, waiting
if necessary until an element becomes available.
Returns |
E |
the head of this deque |
takeLast
public abstract E takeLast ()
Retrieves and removes the last element of this deque, waiting
if necessary until an element becomes available.
Returns |
E |
the tail of this deque |