Package org.eclipse.rdf4j.common.iteration

Class LookAheadIteration<E,X extends Exception>

java.lang.Object

org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration<E,X>

org.eclipse.rdf4j.common.iteration.LookAheadIteration<E,X>

All Implemented Interfaces:

AutoCloseable, CloseableIteration<E,X>, Iteration<E,X>

Direct Known Subclasses:

BottomUpJoinIterator, CrossProductIteration, DescribeIteration, DistinctModelReducingUnionIteration, FilteringIteration, HashJoinIteration, IndependentJoingroupBindingsIteration, IndependentJoingroupBindingsIteration2, IndependentJoingroupBindingsIteration3, JoinExecutorBase, JoinIterator, LeftJoinIterator, MemStatementIterator, MultiProjectionIterator, ParallelExecutorBase, ParallelServiceExecutor, PathIteration, QueueIteration, SPARQLCrossProductIteration, UnionIteration, ZeroLengthPathIteration

public abstract class LookAheadIteration<E,X extends Exception>
extends AbstractCloseableIteration<E,X>

An Iteration that looks one element ahead, if necessary, to handle calls to hasNext(). This is a convenient super class for Iterations that have no easy way to tell if there are any more results, but still should implement the java.util.Iteration interface.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	LookAheadIteration()

Method Summary

Modifier and Type	Method	Description
protected abstract E	getNextElement()	Gets the next element.
protected void	handleClose()	Called by AbstractCloseableIteration.close() when it is called for the first time.
boolean	hasNext()	Returns true if the iteration has more elements.
E	next()	Returns the next element in the iteration.
void	remove()	Throws an UnsupportedOperationException.

Methods inherited from class org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration

close, isClosed

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eclipse.rdf4j.common.iteration.Iteration

stream

Constructor Details

LookAheadIteration

protected LookAheadIteration()

Method Details

getNextElement

protected abstract E getNextElement()
                             throws X

Gets the next element. Subclasses should implement this method so that it returns the next element.

Returns:

The next element, or null if no more elements are available.

Throws:

X extends Exception

hasNext

public final boolean hasNext()
                      throws X

Description copied from interface: Iteration

Returns true if the iteration has more elements. (In other words, returns true if Iteration.next() would return an element rather than throwing a NoSuchElementException.)

Returns:

true if the iteration has more elements.

Throws:

X

next

public final E next()
             throws X

Description copied from interface: Iteration

Returns the next element in the iteration.

Returns:

the next element in the iteration.

Throws:

X extends Exception

remove

public void remove()

Throws an UnsupportedOperationException.

handleClose

protected void handleClose()
                    throws X

Description copied from class: AbstractCloseableIteration

Called by AbstractCloseableIteration.close() when it is called for the first time. This method is only called once on each iteration. By default, this method does nothing.

Overrides:

handleClose in class AbstractCloseableIteration<E,X extends Exception>

Throws:

X