edu.emory.mathcs.backport.java.util.concurrent
public class SynchronousQueue extends AbstractQueue implements BlockingQueue, java.io.Serializable
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 and Description |
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SynchronousQueue()
Creates a SynchronousQueue with nonfair access policy.
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SynchronousQueue(boolean fair)
Creates a SynchronousQueue with specified fairness policy.
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Modifier and Type | Method and Description |
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void |
clear()
Does nothing.
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boolean |
contains(java.lang.Object o)
Always returns false.
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boolean |
containsAll(java.util.Collection c)
Returns false unless the given collection is empty.
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int |
drainTo(java.util.Collection c)
Removes all available elements from this queue and adds them
to the given collection.
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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.
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boolean |
isEmpty()
Always returns true.
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java.util.Iterator |
iterator()
Returns an empty iterator in which hasNext always returns
false.
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boolean |
offer(java.lang.Object e)
Inserts the specified element into this queue, if another thread is
waiting to receive it.
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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.
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java.lang.Object |
peek()
Always returns null.
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java.lang.Object |
poll()
Retrieves and removes the head of this queue, if another thread
is currently making an element available.
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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.
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void |
put(java.lang.Object e)
Adds the specified element to this queue, waiting if necessary for
another thread to receive it.
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int |
remainingCapacity()
Always returns zero.
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boolean |
remove(java.lang.Object o)
Always returns false.
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boolean |
removeAll(java.util.Collection c)
Always returns false.
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boolean |
retainAll(java.util.Collection c)
Always returns false.
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int |
size()
Always returns zero.
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java.lang.Object |
take()
Retrieves and removes the head of this queue, waiting if necessary
for another thread to insert it.
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java.lang.Object[] |
toArray()
Returns a zero-length array.
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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.
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add, addAll, element, remove
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
add
public SynchronousQueue()
public SynchronousQueue(boolean fair)
fair
- if true, threads contend in FIFO order for access;
otherwise the order is unspecified.public void put(java.lang.Object e) throws java.lang.InterruptedException
put
in interface BlockingQueue
e
- the element to addjava.lang.InterruptedException
- if interrupted while waitingjava.lang.NullPointerException
- if the specified element is nullpublic boolean offer(java.lang.Object e, long timeout, TimeUnit unit) throws java.lang.InterruptedException
offer
in interface BlockingQueue
e
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterjava.lang.InterruptedException
- if interrupted while waitingjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object take() throws java.lang.InterruptedException
take
in interface BlockingQueue
java.lang.InterruptedException
- if interrupted while waitingpublic java.lang.Object poll(long timeout, TimeUnit unit) throws java.lang.InterruptedException
poll
in interface BlockingQueue
timeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterjava.lang.InterruptedException
- if interrupted while waitingpublic boolean offer(java.lang.Object e)
offer
in interface BlockingQueue
offer
in interface Queue
e
- the element to addjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object poll()
public boolean isEmpty()
isEmpty
in interface java.util.Collection
isEmpty
in class java.util.AbstractCollection
public int size()
size
in interface java.util.Collection
size
in class java.util.AbstractCollection
public int remainingCapacity()
remainingCapacity
in interface BlockingQueue
public void clear()
clear
in interface java.util.Collection
clear
in class AbstractQueue
public boolean contains(java.lang.Object o)
contains
in interface BlockingQueue
contains
in interface java.util.Collection
contains
in class java.util.AbstractCollection
o
- object to be checked for containment in this queuepublic boolean remove(java.lang.Object o)
remove
in interface BlockingQueue
remove
in interface java.util.Collection
remove
in class java.util.AbstractCollection
o
- the element to removepublic boolean containsAll(java.util.Collection c)
containsAll
in interface java.util.Collection
containsAll
in class java.util.AbstractCollection
c
- the collectionjava.lang.NullPointerException
- if the specified collection is nullpublic boolean removeAll(java.util.Collection c)
removeAll
in interface java.util.Collection
removeAll
in class java.util.AbstractCollection
c
- the collectionpublic boolean retainAll(java.util.Collection c)
retainAll
in interface java.util.Collection
retainAll
in class java.util.AbstractCollection
c
- the collectionpublic java.lang.Object peek()
public java.util.Iterator iterator()
iterator
in interface java.lang.Iterable
iterator
in interface java.util.Collection
iterator
in class java.util.AbstractCollection
public java.lang.Object[] toArray()
toArray
in interface java.util.Collection
toArray
in class AbstractCollection
public java.lang.Object[] toArray(java.lang.Object[] a)
toArray
in interface java.util.Collection
toArray
in class AbstractCollection
a
- the arrayjava.lang.NullPointerException
- if the specified array is nullpublic int drainTo(java.util.Collection c)
BlockingQueue
drainTo
in interface BlockingQueue
c
- the collection to transfer elements intojava.lang.UnsupportedOperationException
- if addition of elements
is not supported by the specified collectionjava.lang.ClassCastException
- if the class of an element of this queue
prevents it from being added to the specified collectionjava.lang.NullPointerException
- if the specified collection is nulljava.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 collectionpublic int drainTo(java.util.Collection c, int maxElements)
BlockingQueue
drainTo
in interface BlockingQueue
c
- the collection to transfer elements intomaxElements
- the maximum number of elements to transferjava.lang.UnsupportedOperationException
- if addition of elements
is not supported by the specified collectionjava.lang.ClassCastException
- if the class of an element of this queue
prevents it from being added to the specified collectionjava.lang.NullPointerException
- if the specified collection is nulljava.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