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FlexDoc/Javadoc 2.0 Demo Java Doc |
Class ArrayDeque<E>
java.util.ArrayDeque<E>
Type Parameters:
E - the type of elements held in this deque
All Implemented Interfaces:
public class ArrayDeque<E>
Resizable-array implementation of the
Deque interface. Array
deques have no capacity restrictions; they grow as necessary to support
usage. They are not thread-safe; in the absence of external
synchronization, they do not support concurrent access by multiple threads.
Null elements are prohibited. This class is likely to be faster than
Stack when used as a stack, and faster than
LinkedList
when used as a queue.
Most ArrayDeque operations run in amortized constant time.
Exceptions include
remove,
removeFirstOccurrence,
removeLastOccurrence,
contains,
iterator.remove(),
and the bulk operations, all of which run in linear time.
The iterators returned by this class's iterator
method are fail-fast: If the deque is modified at any time after
the iterator is created, in any way except through the iterator's own
remove method, the iterator will generally throw a ConcurrentModificationException. Thus, in the face of concurrent
modification, the iterator fails quickly and cleanly, rather than risking
arbitrary, non-deterministic behavior at an undetermined time in the
future.
Note that the fail-fast behavior of an iterator cannot be guaranteed
as it is, generally speaking, impossible to make any hard guarantees in the
presence of unsynchronized concurrent modification. Fail-fast iterators
throw ConcurrentModificationException on a best-effort basis.
Therefore, it would be wrong to write a program that depended on this
exception for its correctness: the fail-fast behavior of iterators
should be used only to detect bugs.
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.
Since:
1.6
Author:
Josh Bloch and Doug Lea
See Also:
Constructor Summary |
Constructs an empty array deque with an initial capacity
sufficient to hold 16 elements.
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Constructs a deque containing the elements of the specified
collection, in the order they are returned by the collection's
iterator.
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Constructs an empty array deque with an initial capacity
sufficient to hold the specified number of elements.
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Method Summary |
boolean |
Inserts the specified element at the end of this deque.
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boolean |
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.
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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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Returns a copy of 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.
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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 deque contains no elements.
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Returns an iterator over the elements in this deque.
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boolean |
Inserts the specified element at the end 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, 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.
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Retrieves and removes the head of the queue represented by this deque.
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boolean |
Removes a single instance 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 in this
deque (when traversing the deque from head to tail).
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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 in this
deque (when traversing the deque from head to tail).
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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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Methods inherited from class java.lang. Object |
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Methods inherited from interface java.util. Collection |
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Constructs an empty array deque with an initial capacity
sufficient to hold 16 elements.
public ArrayDeque |
(int numElements) |
Constructs an empty array deque with an initial capacity
sufficient to hold the specified number of elements.
Parameters:
numElements - lower bound on initial capacity of the deque
Constructs a deque containing the elements of the specified
collection, in the order they are returned by the collection's
iterator. (The first element returned by the collection's
iterator becomes the first element, or
front of the
deque.)
Parameters:
c - the collection whose elements are to be placed into the deque
Throws:
Inserts the specified element at the front of this deque.
Specified by:
Parameters:
e - the element to add
Throws:
Inserts the specified element at the end of this deque.
This method is equivalent to add(E).
Specified by:
Parameters:
e - the element to add
Throws:
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.
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:
public boolean offerFirst |
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Inserts the specified element at the front of this deque.
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
Inserts the specified element at the end of this deque.
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
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:
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, 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, 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
public boolean removeFirstOccurrence |
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Removes the first occurrence of the specified element in this
deque (when traversing the deque from head to tail).
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
public boolean removeLastOccurrence |
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Removes the last occurrence of the specified element in this
deque (when traversing the deque from head to tail).
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
Inserts the specified element at the end of this deque.
This method is equivalent to addLast(E).
Specified by:
Overrides:
Parameters:
e - the element to add
Returns:
Throws:
Inserts the specified element at the end of this deque.
This method is equivalent to offerLast(E).
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
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().
Specified by:
Returns:
the head of the queue represented by this deque
Throws:
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 pollFirst().
Specified by:
Returns:
the head of the queue represented by this deque, or
null if this deque is empty
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().
Specified by:
Returns:
the head of the queue represented by this deque
Throws:
Retrieves, but does not remove, the head of the queue represented by
this deque, or returns
null if this deque is empty.
This method is equivalent to peekFirst().
Specified by:
Returns:
the head of the queue represented by this deque, or
null if this deque is empty
Pushes an element onto the stack represented by this deque. In other
words, inserts the element at the front of this deque.
This method is equivalent to addFirst(E).
Specified by:
Parameters:
e - the element to push
Throws:
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().
Specified by:
Returns:
the element at the front of this deque (which is the top
of the stack represented by this deque)
Throws:
Returns the number of elements in this deque.
Specified by:
Overrides:
Returns:
the number of elements in this deque
public boolean isEmpty |
() |
Returns
true if this deque contains no elements.
Specified by:
Overrides:
Returns:
true if this deque contains no elements
Returns an iterator over the elements in this deque. The elements
will be ordered from first (head) to last (tail). This is the same
order that elements would be dequeued (via successive calls to
remove() or popped (via successive calls to
pop()).
Specified by:
Overrides:
Returns:
an iterator over the elements in this deque
Description copied from interface:
Deque
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).
Specified by:
Returns:
an iterator over the elements in this deque in reverse
sequence
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:
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:
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 - object to be checked for containment in this deque
Returns:
true if this deque contains the specified element
Removes a single instance 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 this deque contained the specified element
Removes all of the elements from this deque.
The deque will be empty after this call returns.
Specified by:
Overrides:
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 a copy of this deque.
Overrides:
Returns:
a copy of this deque
See Also:
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