org.openrdf.sail.federation.evaluation

Class QueueCursor<E>

java.lang.Object

info.aduna.iteration.CloseableIterationBase<E,X>

info.aduna.iteration.LookAheadIteration<E,QueryEvaluationException>

org.openrdf.sail.federation.evaluation.QueueCursor<E>

All Implemented Interfaces:

CloseableIteration<E,QueryEvaluationException>, Iteration<E,QueryEvaluationException>

public class QueueCursor<E>
extends LookAheadIteration<E,QueryEvaluationException>

Makes working with a queue easier by adding the methods done() and toss(Exception) and automatically converting the exception into a QueryEvaluationException with an appropriate stack trace.

Author:

James Leigh

Constructor Summary

Constructors

Constructor and Description
QueueCursor(int capacity) Creates an QueueCursor with the given (fixed) capacity and default access policy.
QueueCursor(int capacity, boolean fair) Creates an QueueCursor with the given (fixed) capacity and the specified access policy.

Method Summary

Methods

Modifier and Type	Method and Description
void	checkException()
void	done() Indicates the method put(Object) will not be called in the queue anymore.
E	getNextElement() Returns the next item in the queue or throws an exception.
void	handleClose()
void	put(E item) Adds another item to the queue, blocking while the queue is full.
void	toss(Exception exception) The next time LookAheadIteration.next() is called this exception will be thrown.

Methods inherited from class info.aduna.iteration.LookAheadIteration

hasNext, next, remove

Methods inherited from class info.aduna.iteration.CloseableIterationBase

close, isClosed

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

QueueCursor

public QueueCursor(int capacity)

Creates an QueueCursor with the given (fixed) capacity and default access policy.

Parameters:

capacity - the capacity of this queue

QueueCursor

public QueueCursor(int capacity,
           boolean fair)

Creates an QueueCursor with the given (fixed) capacity and the specified access policy.

Parameters:

capacity - the capacity of this queue

fair - if true then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; if false the access order is unspecified.

Method Detail

toss

public void toss(Exception exception)

The next time LookAheadIteration.next() is called this exception will be thrown. If it is not a QueryEvaluationException or RuntimeException it will be wrapped in a QueryEvaluationException.

put

public void put(E item)
         throws InterruptedException

Adds another item to the queue, blocking while the queue is full.

Throws:

InterruptedException

done

public void done()

Indicates the method put(Object) will not be called in the queue anymore.

getNextElement

public E getNextElement()
                 throws QueryEvaluationException

Returns the next item in the queue or throws an exception.

Specified by:

getNextElement in class LookAheadIteration<E,QueryEvaluationException>

Throws:

QueryEvaluationException

handleClose

public void handleClose()
                 throws QueryEvaluationException

Overrides:

handleClose in class LookAheadIteration<E,QueryEvaluationException>

Throws:

QueryEvaluationException

checkException

public void checkException()
                    throws QueryEvaluationException

Throws:

QueryEvaluationException