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FlexDoc/Javadoc 2.0 Demo Java Doc |
Interface Deque<E>
Type Parameters:
E - the type of elements held in this deque
All Superinterfaces:
All Known Subinterfaces:
All Known Implementing Classes:
public interface Deque<E>
A linear collection that supports element insertion and removal at
both ends. The name
deque is short for "double ended queue"
and is usually pronounced "deck". Most
Deque
implementations place no fixed limits on the number of elements
they may contain, but this interface supports capacity-restricted
deques as well as those with no fixed size limit.
This interface defines methods to access the elements at both
ends of the deque. Methods are provided to insert, remove, and
examine the element. Each of these methods exists in two forms:
one throws an exception if the operation fails, the other returns a
special value (either null or false, depending on
the operation). The latter form of the insert operation is
designed specifically for use with capacity-restricted
Deque implementations; in most implementations, insert
operations cannot fail.
The twelve methods described above are summarized in the
following table:
This interface extends the Queue interface. When a deque is
used as a queue, FIFO (First-In-First-Out) behavior results. Elements are
added at the end of the deque and removed from the beginning. The methods
inherited from the Queue interface are precisely equivalent to
Deque methods as indicated in the following table:
Deques can also be used as LIFO (Last-In-First-Out) stacks. This
interface should be used in preference to the legacy Stack class.
When a deque is used as a stack, elements are pushed and popped from the
beginning of the deque. Stack methods are equivalent to Deque
methods as indicated in the table below:
Note that the peek method works equally well when
a deque is used as a queue or a stack; in either case, elements are
drawn from the beginning of the deque.
This interface provides two methods to remove interior
elements, removeFirstOccurrence and
removeLastOccurrence.
Unlike the List interface, this interface does not
provide support for indexed access to elements.
While Deque implementations are not strictly required
to prohibit the insertion of null elements, they are strongly
encouraged to do so. Users of any Deque implementations
that do allow null elements are strongly encouraged not to
take advantage of the ability to insert nulls. This is so because
null is used as a special return value by various methods
to indicate that the deque is empty.
Deque implementations generally do not define
element-based versions of the equals and hashCode
methods, but instead inherit the identity-based versions from class
Object.
This interface is a member of the
Java Collections Framework.
Since:
1.6
Author:
Doug Lea, Josh Bloch
Method Summary |
boolean |
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.
|
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.
|
void |
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.
|
void |
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.
|
boolean |
Returns true if this deque contains the specified element.
|
|
Returns an iterator over the elements in this deque in reverse
sequential order.
|
|
Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first element of this deque).
|
|
Retrieves, but does not remove, the first element of this deque.
|
|
Retrieves, but does not remove, the last element of this deque.
|
|
Returns an iterator over the elements in this deque in proper sequence.
|
boolean |
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.
|
boolean |
Inserts the specified element at the front of this deque unless it would
violate capacity restrictions.
|
boolean |
Inserts the specified element at the end of this deque unless it would
violate capacity restrictions.
|
|
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.
|
|
Retrieves, but does not remove, the first element of this deque,
or returns null if this deque is empty.
|
|
Retrieves, but does not remove, the last element of this deque,
or returns null if this deque is empty.
|
|
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.
|
|
Retrieves and removes the first element of this deque,
or returns null if this deque is empty.
|
|
Retrieves and removes the last element of this deque,
or returns null if this deque is empty.
|
|
Pops an element from the stack represented by this deque.
|
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.
|
|
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
|
boolean |
Removes the first occurrence of the specified element from this deque.
|
|
Retrieves and removes the first element of this deque.
|
boolean |
Removes the first occurrence of the specified element from this deque.
|
|
Retrieves and removes the last element of this deque.
|
boolean |
Removes the last occurrence of the specified element from this deque.
|
int |
Returns the number of elements in this deque.
|
Methods inherited from interface java.util. Collection |
clear, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArray |
Methods inherited from interface java.lang. Iterable |
|
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 method
offerFirst(E).
Parameters:
e - the element to add
Throws:
IllegalStateException - if the element cannot be added at this
time due to capacity restrictions
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
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 method
offerLast(E).
This method is equivalent to add(E).
Parameters:
e - the element to add
Throws:
IllegalStateException - if the element cannot be added at this
time due to capacity restrictions
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
Inserts the specified element at the front of this deque unless it would
violate capacity restrictions. When using a capacity-restricted deque,
this method is generally preferable to the
addFirst(E) method,
which can fail to insert an element only by throwing an exception.
Parameters:
e - the element to add
Returns:
true if the element was added to this deque, else
false
Throws:
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
Inserts the specified element at the end of this deque unless it would
violate capacity restrictions. When using a capacity-restricted deque,
this method is generally preferable to the
addLast(E) method,
which can fail to insert an element only by throwing an exception.
Parameters:
e - the element to add
Returns:
true if the element was added to this deque, else
false
Throws:
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
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:
the head of this deque
Throws:
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:
the tail of this deque
Throws:
Retrieves and removes the first element of this deque,
or returns
null if this deque is empty.
Returns:
the head of this deque, or null if this deque is empty
Retrieves and removes the last element of this deque,
or returns
null if this deque is empty.
Returns:
the tail of this deque, or null if this deque is empty
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:
the head of this deque
Throws:
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:
the tail of this deque
Throws:
Retrieves, but does not remove, the first element of this deque,
or returns
null if this deque is empty.
Returns:
the head of this deque, or null if this deque is empty
Retrieves, but does not remove, the last element of this deque,
or returns
null if this deque is empty.
Returns:
the tail of this deque, or null if this deque is empty
boolean removeFirstOccurrence |
|
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
Objects.equals(o, 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 - element to be removed from this deque, if present
Returns:
true if an element was removed as a result of this call
Throws:
boolean removeLastOccurrence |
|
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
Objects.equals(o, 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 - element to be removed from this deque, if present
Returns:
true if an element was removed as a result of this call
Throws:
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(E).
Specified by:
Parameters:
e - the element to add
Returns:
Throws:
IllegalStateException - if the element cannot be added at this
time due to capacity restrictions
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
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(E).
Specified by:
Parameters:
e - the element to add
Returns:
true if the element was added to this deque, else
false
Throws:
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
Retrieves and removes the head of the queue represented by this deque
(in other words, the first element of this deque).
This method differs from
poll() only in that it
throws an exception if this deque is empty.
This method is equivalent to removeFirst().
Specified by:
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 first element of this deque, or null if
this deque is empty
Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first element of this deque).
This method differs from
peek only in that it throws an
exception if this deque is empty.
This method is equivalent to getFirst().
Specified by:
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 (in other words, the first element of this deque), or
returns
null if this deque is empty.
This method is equivalent to peekFirst().
Specified by:
Returns:
the head of the queue represented by this deque, or
null if this deque is empty
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.
When using a capacity-restricted deque, it is generally preferable
to call offer separately on each element.
An exception encountered while trying to add an element may result
in only some of the elements having been successfully added when
the associated exception is thrown.
Specified by:
Parameters:
c - the elements to be inserted into this deque
Returns:
true if this deque changed as a result of the call
Throws:
IllegalStateException - if not all the elements can be added at
this time due to insertion restrictions
ClassCastException - if the class of an element of the specified
collection prevents it from being added to this deque
NullPointerException - if the specified collection contains a
null element and this deque does not permit null elements,
or if the specified collection is null
IllegalArgumentException - if some property of an element of the
specified collection prevents it from being added to this deque
See Also:
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(E).
Parameters:
e - the element to push
Throws:
IllegalStateException - if the element cannot be added at this
time due to capacity restrictions
ClassCastException - if the class of the specified element
prevents it from being added to this deque
NullPointerException - if the specified element is null and this
deque does not permit null elements
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:
the element at the front of this deque (which is the top
of the stack represented by this deque)
Throws:
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
Objects.equals(o, 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:
Parameters:
o - element to be removed from this deque, if present
Returns:
true if an element was removed as a result of this call
Throws:
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
Objects.equals(o, e).
Specified by:
Parameters:
o - element whose presence in this deque is to be tested
Returns:
true if this deque contains the specified element
Throws:
Returns the number of elements in this deque.
Specified by:
Returns:
the number of elements 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).
Specified by:
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).
Returns:
an iterator over the elements in this deque in reverse
sequence
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