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Class ConcurrentLinkedDeque<E>
java.util.concurrent.ConcurrentLinkedDeque<E>
Type Parameters:
E - the type of elements held in this deque
All Implemented Interfaces:
public class ConcurrentLinkedDeque<E>
An unbounded concurrent
deque based on linked nodes.
Concurrent insertion, removal, and access operations execute safely
across multiple threads.
A
ConcurrentLinkedDeque is an appropriate choice when
many threads will share access to a common collection.
Like most other concurrent collection implementations, this class
does not permit the use of
null elements.
Iterators and spliterators are
weakly consistent.
Beware that, unlike in most collections, the size method
is NOT a constant-time operation. Because of the
asynchronous nature of these deques, determining the current number
of elements requires a traversal of the elements, and so may report
inaccurate results if this collection is modified during traversal.
Bulk operations that add, remove, or examine multiple elements,
such as addAll(Collection), removeIf(Predicate) or forEach(Consumer),
are not guaranteed to be performed atomically.
For example, a forEach traversal concurrent with an
addAll operation might observe only some of the added elements.
This class and its iterator implement all of the optional
methods of the Deque and Iterator interfaces.
Memory consistency effects: As with other concurrent collections,
actions in a thread prior to placing an object into a
ConcurrentLinkedDeque
happen-before
actions subsequent to the access or removal of that element from
the ConcurrentLinkedDeque in another thread.
This class is a member of the
Java Collections Framework.
Since:
1.7
Author:
Doug Lea, Martin Buchholz
See Also:
Constructor Summary |
Constructs an empty deque.
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Constructs a deque initially containing the elements of
the given collection, added in traversal order of the
collection's iterator.
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Method Summary |
boolean |
Inserts the specified element at the tail of this deque.
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boolean |
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.
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void |
Inserts the specified element at the front of this deque.
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void |
Inserts the specified element at the end of this deque.
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void |
Removes all of the elements from this deque.
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boolean |
Returns true if this deque contains the specified element.
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Returns an iterator over the elements in this deque in reverse
sequential order.
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Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first element of this deque).
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void |
Performs the given action for each element of the Iterable
until all elements have been processed or the action throws an
exception.
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Retrieves, but does not remove, the first element of this deque.
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Retrieves, but does not remove, the last element of this deque.
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boolean |
Returns true if this collection contains no elements.
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Returns an iterator over the elements in this deque in proper sequence.
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boolean |
Inserts the specified element at the tail of this deque.
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boolean |
Inserts the specified element at the front of this deque.
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boolean |
Inserts the specified element at the end of this deque.
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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.
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Retrieves, but does not remove, the first element of this deque,
or returns null if this deque is empty.
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Retrieves, but does not remove, the last element of this deque,
or returns null if this deque is empty.
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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.
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Retrieves and removes the first element of this deque,
or returns null if this deque is empty.
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Retrieves and removes the last element of this deque,
or returns null if this deque is empty.
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Pops an element from the stack represented by this deque.
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void |
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.
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Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
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boolean |
Removes the first occurrence of the specified element from this deque.
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boolean |
Removes all of this collection's elements that are also contained in the
specified collection (optional operation).
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Retrieves and removes the first element of this deque.
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boolean |
Removes the first occurrence of the specified element from this deque.
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boolean |
Removes all of the elements of this collection that satisfy the given
predicate.
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Retrieves and removes the last element of this deque.
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boolean |
Removes the last occurrence of the specified element from this deque.
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boolean |
Retains only the elements in this collection that are contained in the
specified collection (optional operation).
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int |
Returns the number of elements in this deque.
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Returns an array containing all of the elements in this deque, in
proper sequence (from first to last element).
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Returns an array containing all of the elements in this deque,
in proper sequence (from first to last element); the runtime
type of the returned array is that of the specified array.
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Returns a string representation of this collection.
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Methods inherited from class java.lang. Object |
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Methods inherited from interface java.util. Collection |
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public ConcurrentLinkedDeque |
() |
Constructs an empty deque.
public ConcurrentLinkedDeque |
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Constructs a deque initially containing the elements of
the given collection, added in traversal order of the
collection's iterator.
Parameters:
c - the collection of elements to initially contain
Throws:
Inserts the specified element at the front of this deque.
As the deque is unbounded, this method will never throw
IllegalStateException.
Specified by:
Parameters:
e - the element to add
Throws:
Inserts the specified element at the end of this deque.
As the deque is unbounded, this method will never throw
IllegalStateException.
This method is equivalent to add(E).
Specified by:
Parameters:
e - the element to add
Throws:
public boolean offerFirst |
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Inserts the specified element at the front of this deque.
As the deque is unbounded, this method will never return
false.
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
Inserts the specified element at the end of this deque.
As the deque is unbounded, this method will never return
false.
This method is equivalent to add(E).
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
Description copied from interface:
Deque
Retrieves, but does not remove, the first element of this deque,
or returns null if this deque is empty.
Specified by:
Returns:
the head of this deque, or null if this deque is empty
Description copied from interface:
Deque
Retrieves, but does not remove, the last element of this deque,
or returns null if this deque is empty.
Specified by:
Returns:
the tail of this deque, or null if this deque is empty
Description copied from interface:
Deque
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.
Specified by:
Returns:
the head of this deque
Throws:
Description copied from interface:
Deque
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.
Specified by:
Returns:
the tail of this deque
Throws:
Description copied from interface:
Deque
Retrieves and removes the first element of this deque,
or returns null if this deque is empty.
Specified by:
Returns:
the head of this deque, or null if this deque is empty
Description copied from interface:
Deque
Retrieves and removes the last element of this deque,
or returns null if this deque is empty.
Specified by:
Returns:
the tail of this deque, or null if this deque is empty
Description copied from interface:
Deque
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.
Specified by:
Returns:
the head of this deque
Throws:
Description copied from interface:
Deque
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.
Specified by:
Returns:
the tail of this deque
Throws:
Inserts the specified element at the tail of this deque.
As the deque is unbounded, this method will never return
false.
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
Inserts the specified element at the tail of this deque.
As the deque is unbounded, this method will never throw
IllegalStateException or return
false.
Specified by:
Overrides:
Parameters:
e - element whose presence in this collection is to be ensured
Returns:
Throws:
Description copied from interface:
Deque
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:
Returns:
the first element of this deque, or null if
this deque is empty
Description copied from interface:
Deque
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 Deque.peekFirst().
Specified by:
Returns:
the head of the queue represented by this deque, or
null if this deque is empty
Description copied from interface:
Deque
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 Deque.removeFirst().
Specified by:
Returns:
the head of the queue represented by this deque
Throws:
Description copied from interface:
Deque
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 Deque.removeFirst().
Specified by:
Returns:
the element at the front of this deque (which is the top
of the stack represented by this deque)
Throws:
Description copied from interface:
Deque
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 Deque.getFirst().
Specified by:
Returns:
the head of the queue represented by this deque
Throws:
Description copied from interface:
Deque
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 Deque.addFirst(E).
Specified by:
Parameters:
e - the element to push
Throws:
NullPointerException - if the specified element is null and this
deque does not permit null elements
public boolean removeFirstOccurrence |
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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:
Parameters:
o - element to be removed from this deque, if present
Returns:
true if the deque contained the specified element
Throws:
public boolean removeLastOccurrence |
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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:
Parameters:
o - element to be removed from this deque, if present
Returns:
true if the deque contained the specified element
Throws:
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:
Overrides:
Parameters:
o - element whose presence in this deque is to be tested
Returns:
true if this deque contains the specified element
public boolean isEmpty |
() |
Returns
true if this collection contains no elements.
Specified by:
Overrides:
Returns:
true if this collection contains no elements
Returns the number of elements in this deque. If this deque
contains more than
Integer.MAX_VALUE elements, it
returns
Integer.MAX_VALUE.
Beware that, unlike in most collections, this method is
NOT a constant-time operation. Because of the
asynchronous nature of these deques, determining the current
number of elements requires traversing them all to count them.
Additionally, it is possible for the size to change during
execution of this method, in which case the returned result
will be inaccurate. Thus, this method is typically not very
useful in concurrent applications.
Specified by:
Overrides:
Returns:
the number of elements in this deque
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(Object).
Specified by:
Overrides:
Parameters:
o - element to be removed from this deque, if present
Returns:
true if the deque contained the specified element
Throws:
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.
Specified by:
Overrides:
Parameters:
c - the elements to be inserted into this deque
Returns:
true if this deque changed as a result of the call
Throws:
See Also:
Removes all of the elements from this deque.
Specified by:
Overrides:
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).
Overrides:
Returns:
a string representation of this collection
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.
Specified by:
Overrides:
Returns:
an array containing all of the elements in this deque
Returns an array containing all of the elements in this deque,
in proper sequence (from first to last element); 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().
Specified by:
Overrides:
Type Parameters:
T - the component type of the array to contain the collection
Parameters:
a - 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:
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
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.
Specified by:
Overrides:
Returns:
an iterator over the elements in this deque in proper sequence
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.
Specified by:
Returns:
an iterator over the elements in this deque in reverse order
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.
Specified by:
Parameters:
filter - a predicate which returns true for elements to be
removed
Returns:
true if any elements were removed
Throws:
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.
Specified by:
Overrides:
Parameters:
c - collection containing elements to be removed from this collection
Returns:
true if this collection changed as a result of the
call
Throws:
NullPointerException - if this collection contains one or more
null elements and the specified collection does not support
null elements
(
optional),
or if the specified collection is null
See Also:
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.
Specified by:
Overrides:
Parameters:
c - collection containing elements to be retained in this collection
Returns:
true if this collection changed as a result of the call
Throws:
NullPointerException - if this collection contains one or more
null elements and the specified collection does not permit null
elements
(
optional),
or if the specified collection is null
See Also:
Description copied from interface:
Iterable
Performs the given action for each element of the
Iterable
until all elements have been processed or the action throws an
exception. Actions are performed in the order of iteration, if that
order is specified. Exceptions thrown by the action are relayed to the
caller.
The behavior of this method is unspecified if the action performs
side-effects that modify the underlying source of elements, unless an
overriding class has specified a concurrent modification policy.
Specified by:
Parameters:
action - The action to be performed for each element
Throws:
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