LinkedBlockingDeque
public
class
LinkedBlockingDeque
extends AbstractQueue<E>
implements
BlockingDeque<E>,
Serializable
java.lang.Object | |||
↳ | java.util.AbstractCollection<E> | ||
↳ | java.util.AbstractQueue<E> | ||
↳ | java.util.concurrent.LinkedBlockingDeque<E> |
An optionally-bounded blocking deque based on linked nodes.
The optional capacity bound constructor argument serves as a
way to prevent excessive expansion. The capacity, if unspecified,
is equal to Integer#MAX_VALUE
. Linked nodes are
dynamically created upon each insertion unless this would bring the
deque above capacity.
Most operations run in constant time (ignoring time spent
blocking). Exceptions include remove
,
removeFirstOccurrence
, removeLastOccurrence
, contains
, iterator.remove()
, and the bulk
operations, all of which run in linear time.
This class and its iterator implement all of the optional
methods of the Collection
and Iterator
interfaces.
This class is a member of the Java Collections Framework.
Summary
Public constructors | |
---|---|
LinkedBlockingDeque()
Creates a |
|
LinkedBlockingDeque(int capacity)
Creates a |
|
LinkedBlockingDeque(Collection<? extends E> c)
Creates a |
Public methods | |
---|---|
boolean
|
add(E e)
Inserts the specified element at the end of this deque unless it would violate capacity restrictions. |
boolean
|
addAll(Collection<? extends E> c)
Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator. |
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 |
void
|
clear()
Atomically removes all of the elements from this deque. |
boolean
|
contains(Object o)
Returns |
Iterator<E>
|
descendingIterator()
Returns an iterator over the elements in this deque in reverse sequential order. |
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. |
int
|
drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them to the given collection. |
E
|
element()
Retrieves, but does not remove, the head of the queue represented by this deque. |
void
|
forEach(Consumer<? super E> action)
|
E
|
getFirst()
Retrieves, but does not remove, the first element of this deque. |
E
|
getLast()
Retrieves, but does not remove, the last element of this deque. |
Iterator<E>
|
iterator()
Returns an iterator over the elements in this deque in proper sequence. |
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
|
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
|
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
|
peekFirst()
Retrieves, but does not remove, the first element of this deque,
or returns |
E
|
peekLast()
Retrieves, but does not remove, the last 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
|
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
|
pollFirst()
Retrieves and removes the first element of this deque,
or returns |
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()
Retrieves and removes the last element of this deque,
or returns |
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. |
E
|
pop()
Pops an element from the stack represented by this deque. |
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. |
int
|
remainingCapacity()
Returns the number of additional elements that this deque can ideally (in the absence of memory or resource constraints) accept without blocking. |
boolean
|
remove(Object o)
Removes the first occurrence of the specified element from this deque. |
E
|
remove()
Retrieves and removes the head of the queue represented by this deque. |
boolean
|
removeAll(Collection<?> c)
Removes all of this collection's elements that are also contained in the specified collection (optional operation). |
E
|
removeFirst()
Retrieves and removes the first element of this deque. |
boolean
|
removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element from this deque. |
boolean
|
removeIf(Predicate<? super E> filter)
Removes all of the elements of this collection that satisfy the given predicate. |
E
|
removeLast()
Retrieves and removes the last element of this deque. |
boolean
|
removeLastOccurrence(Object o)
Removes the last occurrence of the specified element from this deque. |
boolean
|
retainAll(Collection<?> c)
Retains only the elements in this collection that are contained in the specified collection (optional operation). |
int
|
size()
Returns the number of elements in this deque. |
Spliterator<E>
|
spliterator()
Returns a |
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. |
Object[]
|
toArray()
Returns an array containing all of the elements in this deque, in proper sequence (from first to last element). |
<T>
T[]
|
toArray(T[] a)
Returns an array containing all of the elements in this deque, in proper sequence; the runtime type of the returned array is that of the specified array. |
String
|
toString()
Returns a string representation of this collection. |
Inherited methods | |
---|---|
Public constructors
LinkedBlockingDeque
public LinkedBlockingDeque ()
Creates a LinkedBlockingDeque
with a capacity of
Integer#MAX_VALUE
.
LinkedBlockingDeque
public LinkedBlockingDeque (int capacity)
Creates a LinkedBlockingDeque
with the given (fixed) capacity.
Parameters | |
---|---|
capacity |
int : the capacity of this deque |
Throws | |
---|---|
IllegalArgumentException |
if capacity is less than 1 |
LinkedBlockingDeque
public LinkedBlockingDeque (Collection<? extends E> c)
Creates a LinkedBlockingDeque
with a capacity of
Integer#MAX_VALUE
, initially containing the elements of
the given collection, added in traversal order of the
collection's iterator.
Parameters | |
---|---|
c |
Collection : the collection of elements to initially contain |
Throws | |
---|---|
NullPointerException |
if the specified collection or any of its elements are null |
Public methods
add
public boolean add (E e)
Inserts the specified element at the end of this deque unless it would
violate capacity restrictions. When using a capacity-restricted deque,
it is generally preferable to use method offer
.
This method is equivalent to addLast(E)
.
Parameters | |
---|---|
e |
E : the element to add |
Returns | |
---|---|
boolean |
true (as specified by Collection#add ) |
Throws | |
---|---|
IllegalStateException |
if this deque is full |
NullPointerException |
if the specified element is null |
addAll
public boolean addAll (Collection<? extends E> c)
Appends all of the elements in the specified collection to the end of
this deque, in the order that they are returned by the specified
collection's iterator. Attempts to addAll
of a deque to
itself result in IllegalArgumentException
.
Parameters | |
---|---|
c |
Collection : the elements to be inserted into this deque |
Returns | |
---|---|
boolean |
true if this deque changed as a result of the call |
Throws | |
---|---|
NullPointerException |
if the specified collection or any of its elements are null |
IllegalArgumentException |
if the collection is this deque |
IllegalStateException |
if this deque is full |
See also:
addFirst
public 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 |
Throws | |
---|---|
IllegalStateException |
if this deque is full |
NullPointerException |
addLast
public 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 |
Throws | |
---|---|
IllegalStateException |
if this deque is full |
NullPointerException |
clear
public void clear ()
Atomically removes all of the elements from this deque. The deque will be empty after this call returns.
contains
public 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 |
descendingIterator
public Iterator<E> descendingIterator ()
Returns an iterator over the elements in this deque in reverse sequential order. The elements will be returned in order from last (tail) to first (head).
The returned iterator is weakly consistent.
Returns | |
---|---|
Iterator<E> |
an iterator over the elements in this deque in reverse order |
drainTo
public 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. A failure
encountered while attempting to add elements to
collection c
may result in elements being in neither,
either or both collections when the associated exception is
thrown. Attempts to drain a queue to itself result in
IllegalArgumentException
. Further, the behavior of
this operation is undefined if the specified collection is
modified while the operation is in progress.
Parameters | |
---|---|
c |
Collection : the collection to transfer elements into |
maxElements |
int : the maximum number of elements to transfer |
Returns | |
---|---|
int |
the number of elements transferred |
Throws | |
---|---|
UnsupportedOperationException |
|
ClassCastException |
|
NullPointerException |
|
IllegalArgumentException |
drainTo
public int drainTo (Collection<? super E> c)
Removes all available elements from this queue and adds them
to the given collection. This operation may be more
efficient than repeatedly polling this queue. A failure
encountered while attempting to add elements to
collection c
may result in elements being in neither,
either or both collections when the associated exception is
thrown. Attempts to drain a queue to itself result in
IllegalArgumentException
. Further, the behavior of
this operation is undefined if the specified collection is
modified while the operation is in progress.
Parameters | |
---|---|
c |
Collection : the collection to transfer elements into |
Returns | |
---|---|
int |
the number of elements transferred |
Throws | |
---|---|
UnsupportedOperationException |
|
ClassCastException |
|
NullPointerException |
|
IllegalArgumentException |
element
public E element ()
Retrieves, but does not remove, the head of the queue represented by
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 the queue represented by this deque |
Throws | |
---|---|
NoSuchElementException |
if this deque is empty |
forEach
public void forEach (Consumer<? super E> action)
Parameters | |
---|---|
action |
Consumer |
Throws | |
---|---|
NullPointerException |
getFirst
public E getFirst ()
Retrieves, but does not remove, the first element of this deque.
This method differs from peekFirst
only in that it
throws an exception if this deque is empty.
Returns | |
---|---|
E |
the head of this deque |
Throws | |
---|---|
NoSuchElementException |
getLast
public E getLast ()
Retrieves, but does not remove, the last element of this deque.
This method differs from peekLast
only in that it
throws an exception if this deque is empty.
Returns | |
---|---|
E |
the tail of this deque |
Throws | |
---|---|
NoSuchElementException |
iterator
public 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).
The returned iterator is weakly consistent.
Returns | |
---|---|
Iterator<E> |
an iterator over the elements in this deque in proper sequence |
offer
public 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 |
Throws | |
---|---|
NullPointerException |
|
InterruptedException |
offer
public 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 |
Throws | |
---|---|
NullPointerException |
if the specified element is null |
offerFirst
public 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 |
Throws | |
---|---|
NullPointerException |
offerFirst
public 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 |
Throws | |
---|---|
NullPointerException |
|
InterruptedException |
offerLast
public 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 |
Throws | |
---|---|
NullPointerException |
offerLast
public 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 |
Throws | |
---|---|
NullPointerException |
|
InterruptedException |
peek
public 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 |
peekFirst
public E peekFirst ()
Retrieves, but does not remove, the first element of this deque,
or returns null
if this deque is empty.
Returns | |
---|---|
E |
the head of this deque, or null if this deque is empty |
peekLast
public E peekLast ()
Retrieves, but does not remove, the last element of this deque,
or returns null
if this deque is empty.
Returns | |
---|---|
E |
the tail of this deque, or null if this deque is empty |
poll
public 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 |
Throws | |
---|---|
InterruptedException |
poll
public 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 E pollFirst ()
Retrieves and removes the first element of this deque,
or returns null
if this deque is empty.
Returns | |
---|---|
E |
the head of this deque, or null if this deque is empty |
pollFirst
public 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 |
Throws | |
---|---|
InterruptedException |
pollLast
public E pollLast ()
Retrieves and removes the last element of this deque,
or returns null
if this deque is empty.
Returns | |
---|---|
E |
the tail of this deque, or null if this deque is empty |
pollLast
public 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 |
Throws | |
---|---|
InterruptedException |
pop
public E pop ()
Pops an element from the stack represented by this deque. In other words, removes and returns the first element of this deque.
This method is equivalent to removeFirst()
.
Returns | |
---|---|
E |
the element at the front of this deque (which is the top of the stack represented by this deque) |
Throws | |
---|---|
NoSuchElementException |
push
public 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 |
Throws | |
---|---|
IllegalStateException |
if this deque is full |
NullPointerException |
put
public 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 |
Throws | |
---|---|
NullPointerException |
|
InterruptedException |
putFirst
public 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 |
Throws | |
---|---|
NullPointerException |
|
InterruptedException |
putLast
public 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 |
Throws | |
---|---|
NullPointerException |
|
InterruptedException |
remainingCapacity
public int remainingCapacity ()
Returns the number of additional elements that this deque can ideally
(in the absence of memory or resource constraints) accept without
blocking. This is always equal to the initial capacity of this deque
less the current size
of this deque.
Note that you cannot always tell if an attempt to insert
an element will succeed by inspecting remainingCapacity
because it may be the case that another thread is about to
insert or remove an element.
Returns | |
---|---|
int |
the remaining capacity |
remove
public 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 |
remove
public E remove ()
Retrieves and removes the head of the queue represented by 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 |
Throws | |
---|---|
NoSuchElementException |
if this deque is empty |
removeAll
public boolean removeAll (Collection<?> c)
Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.
Parameters | |
---|---|
c |
Collection : collection containing elements to be removed from this collection |
Returns | |
---|---|
boolean |
true if this collection changed as a result of the
call |
Throws | |
---|---|
NullPointerException |
removeFirst
public E removeFirst ()
Retrieves and removes the first element of this deque. This method
differs from pollFirst
only in that it throws an
exception if this deque is empty.
Returns | |
---|---|
E |
the head of this deque |
Throws | |
---|---|
NoSuchElementException |
removeFirstOccurrence
public 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 |
removeIf
public boolean removeIf (Predicate<? super E> filter)
Removes all of the elements of this collection that satisfy the given predicate. Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller.
Parameters | |
---|---|
filter |
Predicate : a predicate which returns true for elements to be
removed |
Returns | |
---|---|
boolean |
true if any elements were removed |
Throws | |
---|---|
NullPointerException |
removeLast
public E removeLast ()
Retrieves and removes the last element of this deque. This method
differs from pollLast
only in that it throws an
exception if this deque is empty.
Returns | |
---|---|
E |
the tail of this deque |
Throws | |
---|---|
NoSuchElementException |
removeLastOccurrence
public 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 |
retainAll
public boolean retainAll (Collection<?> c)
Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.
Parameters | |
---|---|
c |
Collection : collection containing elements to be retained in this collection |
Returns | |
---|---|
boolean |
true if this collection changed as a result of the call |
Throws | |
---|---|
NullPointerException |
size
public int size ()
Returns the number of elements in this deque.
Returns | |
---|---|
int |
the number of elements in this deque |
spliterator
public Spliterator<E> spliterator ()
Returns a Spliterator
over the elements in this deque.
The returned spliterator is weakly consistent.
The Spliterator
reports Spliterator#CONCURRENT
,
Spliterator#ORDERED
, and Spliterator#NONNULL
.
Implementation Note:
- The
Spliterator
implementstrySplit
to permit limited parallelism.
Returns | |
---|---|
Spliterator<E> |
a Spliterator over the elements in this deque |
take
public 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 |
Throws | |
---|---|
InterruptedException |
takeFirst
public 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 |
Throws | |
---|---|
InterruptedException |
takeLast
public 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 |
Throws | |
---|---|
InterruptedException |
toArray
public Object[] toArray ()
Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).
The returned array will be "safe" in that no references to it are maintained by this deque. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
Returns | |
---|---|
Object[] |
an array containing all of the elements in this deque |
toArray
public T[] toArray (T[] a)
Returns an array containing all of the elements in this deque, in proper sequence; the runtime type of the returned array is that of the specified array. If the deque fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this deque.
If this deque fits in the specified array with room to spare
(i.e., the array has more elements than this deque), the element in
the array immediately following the end of the deque is set to
null
.
Like the toArray()
method, this method acts as bridge between
array-based and collection-based APIs. Further, this method allows
precise control over the runtime type of the output array, and may,
under certain circumstances, be used to save allocation costs.
Suppose x
is a deque known to contain only strings.
The following code can be used to dump the deque into a newly
allocated array of String
:
String[] y = x.toArray(new String[0]);
Note that toArray(new Object[0])
is identical in function to
toArray()
.
Parameters | |
---|---|
a |
T : the array into which the elements of the deque are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purpose |
Returns | |
---|---|
T[] |
an array containing all of the elements in this deque |
Throws | |
---|---|
ArrayStoreException |
if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque |
NullPointerException |
if the specified array is null |
toString
public String toString ()
Returns a string representation of this collection. The string
representation consists of a list of the collection's elements in the
order they are returned by its iterator, enclosed in square brackets
("[]"
). Adjacent elements are separated by the characters
", "
(comma and space). Elements are converted to strings as
by String#valueOf(Object)
.
Returns | |
---|---|
String |
a string representation of this collection |