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java.util
Class AbstractQueue<E>
java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
-
-
Type Parameters:
-
E - the type of elements held in this collection
-
All Implemented Interfaces:
-
Iterable
<E>,
Collection
<E>,
Queue
<E>
-
Direct Known Subclasses:
-
ArrayBlockingQueue
,
ConcurrentLinkedQueue
,
DelayQueue
,
LinkedBlockingDeque
,
LinkedBlockingQueue
,
PriorityBlockingQueue
,
PriorityQueue
,
SynchronousQueue
-
public abstract class AbstractQueue<E>
- extends AbstractCollection<E>
- implements Queue<E>
This class provides skeletal implementations of some
Queue
operations. The implementations in this class are appropriate when the base implementation does not allow
null
elements. Methods
add
,
remove
, and
element
are based on
offer
,
poll
, and
peek
, respectively but throw exceptions instead of indicating failure via
false
or
null
returns.
A
Queue
implementation that extends this class must minimally define a method
Queue.offer(E)
which does not permit insertion of
null
elements, along with methods
Queue.peek()
,
Queue.poll()
,
Collection.size()
, and a
Collection.iterator()
supporting
Iterator.remove()
. Typically, additional methods will be overridden as well. If these requirements cannot be met, consider instead subclassing
AbstractCollection
.
This class is a member of the
Java Collections Framework
.
-
Since:
-
1.5
Constructor Summary
|
protected |
AbstractQueue
()
Constructor for use by subclasses. |
Method Summary
|
boolean |
add
(
E
Inserts
Adds
the specified element
into
to
this
queue if it is possible to do so immediately without violating capacity restrictions, returning
true
upon success and throwing an
IllegalStateException
if no space is currently available.
queue.
|
boolean |
addAll
(
Collection
<? extends
E
> c)
Adds all of the elements in the specified collection to this queue. |
void |
clear
()
Removes all of the elements from this
queue.
collection.
|
E
|
element
()
Retrieves, but does not remove, the head of this queue. |
E
|
remove
()
Retrieves and removes the head of this queue. |
Methods inherited from class java.util.
AbstractCollection
|
contains
,
containsAll
,
isEmpty
,
iterator
,
remove
,
removeAll
,
retainAll
,
size
,
toArray
,
toArray
,
toString
|
Methods inherited from interface java.util.
Collection
|
contains
,
containsAll
,
equals
,
hashCode
,
isEmpty
,
iterator
,
remove
,
removeAll
,
retainAll
,
size
,
toArray
,
toArray
|
AbstractQueue
protected AbstractQueue()
-
Constructor for use by subclasses.
add
public boolean add(E e) o)
-
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning
true
upon success and throwing an
IllegalStateException
if no space is currently available.
Adds the specified element to this queue.
This implementation returns
true
if
offer
succeeds, else throws an
IllegalStateException
.
IllegalStateException.
-
-
Specified by:
-
add
in interface
Collection
<
E
>
-
Specified by:
-
add
in interface
Queue
<
E
>
-
Overrides:
-
add
in class
AbstractCollection
<
E
>
-
-
Parameters:
-
e
o
- the element
to add
-
Returns:
-
true
(as specified by
Collection.add(E)
)
(as per the general contract of
Collection.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 queue
-
NullPointerException
- if the specified element is
null
and this queue not permit null elements
-
IllegalArgumentException
IllegalStateException
- if some property of this element prevents it from being added to this queue
- if element cannot be added
remove
public E remove()
-
Retrieves and removes the head of this queue.
This method differs from
poll
only in that it throws an exception if this queue is empty.
This implementation returns the result of
poll
unless the queue is empty.
-
-
Specified by:
-
remove
in interface
Queue
<
E
>
-
-
Returns:
-
the head of this
queue
queue.
-
Throws:
-
NoSuchElementException
- if this queue is
empty
empty.
element
public E element()
-
Retrieves, but does not remove, the head of this queue.
This method differs from
peek
only in that it throws an exception if this queue is empty.
This implementation returns the result of
peek
unless the queue is empty.
-
-
Specified by:
-
element
in interface
Queue
<
E
>
-
-
Returns:
-
the head of this
queue
queue.
-
Throws:
-
NoSuchElementException
- if this queue is
empty
empty.
clear
public void clear()
-
Removes all of the elements from this
queue.
collection.
The
queue
collection
will be empty after this call returns.
This implementation repeatedly invokes
poll
until it returns
null
.
-
-
Specified by:
-
clear
in interface
Collection
<
E
>
-
Overrides:
-
clear
in class
AbstractCollection
<
E
>
-
addAll
public boolean addAll(Collection<? extends E> c)
-
Adds all of the elements in the specified collection to this queue. Attempts to addAll of 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.
This implementation iterates over the specified collection, and adds each element returned by the iterator to this
queue,
collection,
in turn. A runtime exception encountered while trying to add an element (including, in particular, a
null
element) may result in only some of the elements having been successfully added when the associated exception is thrown.
-
-
Specified by:
-
addAll
in interface
Collection
<
E
>
-
Overrides:
-
addAll
in class
AbstractCollection
<
E
>
-
-
Parameters:
-
c - collection
containing
whose
elements
are
to be added to this
queue
collection.
-
Returns:
-
true
if this
queue
collection
changed as a result of the
call
call.
-
Throws:
-
ClassCastException
- if the class of an element of the specified collection prevents it from being added to this queue
-
NullPointerException
- if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null
- if the specified collection or any of its elements are null.
-
IllegalArgumentException
- if some property of an element of the specified collection prevents it from being added to this queue, or if the specified collection is this queue
-
IllegalStateException
- if not all the elements can be added at this time due to insertion restrictions
- if c is this queue.
-
See Also:
-
add(Object)