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Java™ Platform Standard Ed. 6 |
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java.lang.Objectjava.util.AbstractCollection<E>
java.util.AbstractQueue<E>
java.util.concurrent.LinkedBlockingQueue<E>
E
- the type of elements held in this collectionpublic class LinkedBlockingQueue<E>
An optionally-bounded blocking queue based on linked nodes. This queue orders elements FIFO (first-in-first-out). The head of the queue is that element that has been on the queue the longest time. The tail of the queue is that element that has been on the queue the shortest time. New elements are inserted at the tail of the queue, and the queue retrieval operations obtain elements at the head of the queue. Linked queues typically have higher throughput than array-based queues but less predictable performance in most concurrent applications.
The optional capacity bound constructor argument serves as a
way to prevent excessive queue expansion. The capacity, if unspecified,
is equal to Integer.MAX_VALUE
. Linked nodes are
dynamically created upon each insertion unless this would bring the
queue above capacity.
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.
Constructor Summary | |
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LinkedBlockingQueue()
Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE . |
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LinkedBlockingQueue(Collection<? extends E> c)
Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE , initially containing the elements of the
given collection,
added in traversal order of the collection's iterator. |
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LinkedBlockingQueue(int capacity)
Creates a LinkedBlockingQueue with the given (fixed) capacity. |
Method Summary | ||
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void |
clear()
Atomically removes all of the elements from this queue. |
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int |
drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them to the given collection. |
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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. |
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Iterator<E> |
iterator()
Returns an iterator over the elements in this queue in proper sequence. |
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boolean |
offer(E e)
Inserts the specified element at the tail of this queue if it is possible to do so immediately without exceeding the queue's capacity, returning true upon success and false if this queue is full. |
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boolean |
offer(E e,
long timeout,
TimeUnit unit)
Inserts the specified element at the tail of this queue, waiting if necessary up to the specified wait time for space to become available. |
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E |
peek()
Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty. |
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E |
poll()
Retrieves and removes the head of this queue, or returns null if this queue is empty. |
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E |
poll(long timeout,
TimeUnit unit)
Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available. |
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void |
put(E e)
Inserts the specified element at the tail of this queue, waiting if necessary for space to become available. |
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int |
remainingCapacity()
Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking. |
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boolean |
remove(Object o)
Removes a single instance of the specified element from this queue, if it is present. |
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int |
size()
Returns the number of elements in this queue. |
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E |
take()
Retrieves and removes the head of this queue, waiting if necessary until an element becomes available. |
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Object[] |
toArray()
Returns an array containing all of the elements in this queue, in proper sequence. |
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toArray(T[] a)
Returns an array containing all of the elements in this queue, in proper sequence; the runtime type of the returned array is that of the specified array. |
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String |
toString()
Returns a string representation of this collection. |
Methods inherited from class java.util.AbstractQueue |
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add, addAll, element, remove |
Methods inherited from class java.util.AbstractCollection |
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contains, containsAll, isEmpty, removeAll, retainAll |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Methods inherited from interface java.util.concurrent.BlockingQueue |
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add, contains |
Methods inherited from interface java.util.Queue |
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element, remove |
Methods inherited from interface java.util.Collection |
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addAll, containsAll, equals, hashCode, isEmpty, removeAll, retainAll |
Constructor Detail |
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public LinkedBlockingQueue()
Integer.MAX_VALUE
.
public LinkedBlockingQueue(int capacity)
capacity
- the capacity of this queue
IllegalArgumentException
- if capacity is not greater
than zeropublic LinkedBlockingQueue(Collection<? extends E> c)
Integer.MAX_VALUE
, initially containing the elements of the
given collection,
added in traversal order of the collection's iterator.
c
- the collection of elements to initially contain
NullPointerException
- if the specified collection or any
of its elements are nullMethod Detail |
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public int size()
size
in interface Collection<E>
size
in class AbstractCollection<E>
public int remainingCapacity()
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.
remainingCapacity
in interface BlockingQueue<E>
public void put(E e) throws InterruptedException
put
in interface BlockingQueue<E>
e
- the element to add
InterruptedException
- if interrupted while waiting
NullPointerException
- if the specified element is nullpublic boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException
offer
in interface BlockingQueue<E>
e
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameter
InterruptedException
- if interrupted while waiting
NullPointerException
- if the specified element is nullpublic boolean offer(E e)
add
, which can fail to
insert an element only by throwing an exception.
offer
in interface BlockingQueue<E>
offer
in interface Queue<E>
e
- the element to add
NullPointerException
- if the specified element is nullpublic E take() throws InterruptedException
BlockingQueue
take
in interface BlockingQueue<E>
InterruptedException
- if interrupted while waitingpublic E poll(long timeout, TimeUnit unit) throws InterruptedException
BlockingQueue
poll
in interface BlockingQueue<E>
timeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameter
InterruptedException
- if interrupted while waitingpublic E poll()
Queue
poll
in interface Queue<E>
public E peek()
Queue
peek
in interface Queue<E>
public boolean remove(Object o)
remove
in interface Collection<E>
remove
in interface BlockingQueue<E>
remove
in class AbstractCollection<E>
o
- element to be removed from this queue, if present
public Object[] toArray()
The returned array will be "safe" in that no references to it are maintained by this queue. (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.
toArray
in interface Collection<E>
toArray
in class AbstractCollection<E>
public <T> T[] toArray(T[] a)
If this queue fits in the specified array with room to spare (i.e., the array has more elements than this queue), the element in the array immediately following the end of the queue 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 queue known to contain only strings. The following code can be used to dump the queue 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().
toArray
in interface Collection<E>
toArray
in class AbstractCollection<E>
a
- the array into which the elements of the queue are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purpose
ArrayStoreException
- if the runtime type of the specified array
is not a supertype of the runtime type of every element in
this queue
NullPointerException
- if the specified array is nullpublic String toString()
AbstractCollection
String.valueOf(Object)
.
toString
in class AbstractCollection<E>
public void clear()
clear
in interface Collection<E>
clear
in class AbstractQueue<E>
public int drainTo(Collection<? super E> c)
BlockingQueue
drainTo
in interface BlockingQueue<E>
c
- the collection to transfer elements into
UnsupportedOperationException
- if addition of elements
is not supported by the specified collection
ClassCastException
- if the class of an element of this queue
prevents it from being added to the specified collection
NullPointerException
- if the specified collection is null
IllegalArgumentException
- if the specified collection is this
queue, or some property of an element of this queue prevents
it from being added to the specified collectionpublic int drainTo(Collection<? super E> c, int maxElements)
BlockingQueue
drainTo
in interface BlockingQueue<E>
c
- the collection to transfer elements intomaxElements
- the maximum number of elements to transfer
UnsupportedOperationException
- if addition of elements
is not supported by the specified collection
ClassCastException
- if the class of an element of this queue
prevents it from being added to the specified collection
NullPointerException
- if the specified collection is null
IllegalArgumentException
- if the specified collection is this
queue, or some property of an element of this queue prevents
it from being added to the specified collectionpublic Iterator<E> iterator()
ConcurrentModificationException
,
and guarantees to traverse elements as they existed upon
construction of the iterator, and may (but is not guaranteed to)
reflect any modifications subsequent to construction.
iterator
in interface Iterable<E>
iterator
in interface Collection<E>
iterator
in class AbstractCollection<E>
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Java™ Platform Standard Ed. 6 |
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