|
||||||||||
| PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
| SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | |||||||||
java.lang.Objectjava.util.AbstractCollection
edu.emory.mathcs.backport.java.util.AbstractCollection
edu.emory.mathcs.backport.java.util.AbstractQueue
edu.emory.mathcs.backport.java.util.concurrent.SynchronousQueue
A blocking queue in which each insert operation must wait for a corresponding remove operation by another thread, and vice versa. A synchronous queue does not have any internal capacity, not even a capacity of one. You cannot peek at a synchronous queue because an element is only present when you try to remove it; you cannot insert an element (using any method) unless another thread is trying to remove it; you cannot iterate as there is nothing to iterate. The head of the queue is the element that the first queued inserting thread is trying to add to the queue; if there is no such queued thread then no element is available for removal and poll() will return null. For purposes of other Collection methods (for example contains), a SynchronousQueue acts as an empty collection. This queue does not permit null elements.
Synchronous queues are similar to rendezvous channels used in CSP and Ada. They are well suited for handoff designs, in which an object running in one thread must sync up with an object running in another thread in order to hand it some information, event, or task.
This class supports an optional fairness policy for ordering waiting producer and consumer threads. By default, this ordering is not guaranteed. However, a queue constructed with fairness set to true grants threads access in FIFO order. Fairness generally decreases throughput but reduces variability and avoids starvation.
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 | |
SynchronousQueue()
Creates a SynchronousQueue with nonfair access policy. |
|
SynchronousQueue(boolean fair)
Creates a SynchronousQueue with specified fairness policy. |
|
| Method Summary | |
void |
clear()
Does nothing. |
boolean |
contains(java.lang.Object o)
Always returns false. |
boolean |
containsAll(java.util.Collection c)
Returns false unless the given collection is empty. |
int |
drainTo(java.util.Collection c)
Removes all available elements from this queue and adds them to the given collection. |
int |
drainTo(java.util.Collection c,
int maxElements)
Removes at most the given number of available elements from this queue and adds them to the given collection. |
boolean |
isEmpty()
Always returns true. |
java.util.Iterator |
iterator()
Returns an empty iterator in which hasNext always returns false. |
boolean |
offer(java.lang.Object e)
Inserts the specified element into this queue, if another thread is waiting to receive it. |
boolean |
offer(java.lang.Object e,
long timeout,
TimeUnit unit)
Inserts the specified element into this queue, waiting if necessary up to the specified wait time for another thread to receive it. |
java.lang.Object |
peek()
Always returns null. |
java.lang.Object |
poll()
Retrieves and removes the head of this queue, if another thread is currently making an element available. |
java.lang.Object |
poll(long timeout,
TimeUnit unit)
Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time, for another thread to insert it. |
void |
put(java.lang.Object e)
Adds the specified element to this queue, waiting if necessary for another thread to receive it. |
int |
remainingCapacity()
Always returns zero. |
boolean |
remove(java.lang.Object o)
Always returns false. |
boolean |
removeAll(java.util.Collection c)
Always returns false. |
boolean |
retainAll(java.util.Collection c)
Always returns false. |
int |
size()
Always returns zero. |
java.lang.Object |
take()
Retrieves and removes the head of this queue, waiting if necessary for another thread to insert it. |
java.lang.Object[] |
toArray()
Returns a zero-length array. |
java.lang.Object[] |
toArray(java.lang.Object[] a)
Sets the zeroeth element of the specified array to null (if the array has non-zero length) and returns it. |
| Methods inherited from class edu.emory.mathcs.backport.java.util.AbstractQueue |
add, addAll, element, remove |
| Methods inherited from class java.util.AbstractCollection |
toString |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface edu.emory.mathcs.backport.java.util.concurrent.BlockingQueue |
add |
| Methods inherited from interface edu.emory.mathcs.backport.java.util.Queue |
element, remove |
| Methods inherited from interface java.util.Collection |
addAll, equals, hashCode |
| Constructor Detail |
public SynchronousQueue()
public SynchronousQueue(boolean fair)
fair - if true, threads contend in FIFO order for access;
otherwise the order is unspecified.| Method Detail |
public void put(java.lang.Object e)
throws java.lang.InterruptedException
put in interface BlockingQueuee - the element to add
java.lang.InterruptedException - if interrupted while waiting
java.lang.NullPointerException - if the specified element is null
public boolean offer(java.lang.Object e,
long timeout,
TimeUnit unit)
throws java.lang.InterruptedException
offer in interface BlockingQueuee - the element to addtimeout - how long to wait before giving up, in units of
unitunit - a TimeUnit determining how to interpret the
timeout parameter
java.lang.InterruptedException - if interrupted while waiting
java.lang.NullPointerException - if the specified element is null
public java.lang.Object take()
throws java.lang.InterruptedException
take in interface BlockingQueuejava.lang.InterruptedException - if interrupted while waiting
public java.lang.Object poll(long timeout,
TimeUnit unit)
throws java.lang.InterruptedException
poll in interface BlockingQueuetimeout - how long to wait before giving up, in units of
unitunit - a TimeUnit determining how to interpret the
timeout parameter
java.lang.InterruptedException - if interrupted while waitingpublic boolean offer(java.lang.Object e)
offer in interface BlockingQueuee - the element to add
java.lang.NullPointerException - if the specified element is nullpublic java.lang.Object poll()
poll in interface Queuepublic boolean isEmpty()
isEmpty in interface java.util.Collectionpublic int size()
size in interface java.util.Collectionpublic int remainingCapacity()
remainingCapacity in interface BlockingQueuepublic void clear()
clear in interface java.util.Collectionclear in class AbstractQueuepublic boolean contains(java.lang.Object o)
contains in interface BlockingQueueo - object to be checked for containment in this queue
public boolean remove(java.lang.Object o)
remove in interface BlockingQueueo - the element to remove
public boolean containsAll(java.util.Collection c)
containsAll in interface java.util.Collectionc - the collection
java.lang.NullPointerException - if the specified collection is nullpublic boolean removeAll(java.util.Collection c)
removeAll in interface java.util.Collectionc - the collection
public boolean retainAll(java.util.Collection c)
retainAll in interface java.util.Collectionc - the collection
public java.lang.Object peek()
peek in interface Queuepublic java.util.Iterator iterator()
iterator in interface java.util.Collectionpublic java.lang.Object[] toArray()
toArray in interface java.util.CollectiontoArray in class AbstractCollectionpublic java.lang.Object[] toArray(java.lang.Object[] a)
toArray in interface java.util.CollectiontoArray in class AbstractCollectiona - the array
java.lang.NullPointerException - if the specified array is nullpublic int drainTo(java.util.Collection c)
BlockingQueue
drainTo in interface BlockingQueuec - the collection to transfer elements into
java.lang.UnsupportedOperationException - if addition of elements
is not supported by the specified collection
java.lang.ClassCastException - if the class of an element of this queue
prevents it from being added to the specified collection
java.lang.NullPointerException - if the specified collection is null
java.lang.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 collection
public int drainTo(java.util.Collection c,
int maxElements)
BlockingQueue
drainTo in interface BlockingQueuec - the collection to transfer elements intomaxElements - the maximum number of elements to transfer
java.lang.UnsupportedOperationException - if addition of elements
is not supported by the specified collection
java.lang.ClassCastException - if the class of an element of this queue
prevents it from being added to the specified collection
java.lang.NullPointerException - if the specified collection is null
java.lang.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 collection
|
||||||||||
| PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
| SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | |||||||||