Package org.eclipse.rdf4j.common.iteration

Class DelayedIteration<E>

java.lang.Object

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

org.eclipse.rdf4j.common.iteration.DelayedIteration<E>

All Implemented Interfaces:

AutoCloseable, Iterator<E>, CloseableIteration<E>

Direct Known Subclasses:

OrderIterator, QueryEvaluationStep.DelayedEvaluationIteration

public abstract class DelayedIteration<E>
extends AbstractCloseableIteration<E>

An iteration that delays the creation of the underlying iteration until it is being accessed. This is mainly useful for situations where iteration creation adds considerable overhead but where the iteration may not actually be used, or where a created iteration consumes scarce resources like JDBC-connections or memory. Subclasses must implement the createIteration method, which is called once when the iteration is first needed.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	DelayedIteration()	Creates a new DelayedIteration.

Method Summary

Modifier and Type	Method	Description
protected abstract CloseableIteration<? extends E>	createIteration()	Creates the iteration that should be iterated over.
protected void	handleClose()	Closes this iteration as well as the underlying iteration if it has already been created and happens to be a CloseableIteration.
boolean	hasNext()	Calls the hasNext method of the underlying iteration.
E	next()	Calls the next method of the underlying iteration.
void	remove()	Calls the remove method of the underlying iteration.

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.CloseableIteration

stream

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Details

DelayedIteration

protected DelayedIteration()

Creates a new DelayedIteration.

Method Details

createIteration

protected abstract CloseableIteration<? extends E> createIteration()

Creates the iteration that should be iterated over. This method is called only once, when the iteration is first needed.

hasNext

public boolean hasNext()

Calls the hasNext method of the underlying iteration.

next

public E next()

Calls the next method of the underlying iteration.

remove

public void remove()

Calls the remove method of the underlying iteration.

handleClose

protected void handleClose()

Closes this iteration as well as the underlying iteration if it has already been created and happens to be a CloseableIteration.

Specified by:

handleClose in class AbstractCloseableIteration<E>