org.eclipse.rdf4j.common.iteration

Class DelayedIteration<E,X extends Exception>

java.lang.Object

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

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

All Implemented Interfaces:

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

Direct Known Subclasses:

OrderIterator

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

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 and Description
protected	DelayedIteration() Creates a new DelayedIteration.

Method Summary

Modifier and Type	Method and Description
protected abstract Iteration<? extends E,? extends X>	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.Iteration

stream

Constructor Detail

DelayedIteration

protected DelayedIteration()

Creates a new DelayedIteration.

Method Detail

createIteration

protected abstract Iteration<? extends E,? extends X> createIteration()
                                                               throws X extends Exception

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

Throws:

X extends Exception

hasNext

public boolean hasNext()
                throws X extends Exception

Calls the hasNext method of the underlying iteration.

Returns:

true if the iteration has more elements.

Throws:

X

X extends Exception

next

public E next()
       throws X extends Exception

Calls the next method of the underlying iteration.

Returns:

the next element in the iteration.

Throws:

X extends Exception

remove

public void remove()
            throws X extends Exception

Calls the remove method of the underlying iteration.

Throws:

X extends Exception

handleClose

protected void handleClose()
                    throws X extends Exception

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

Overrides:

handleClose in class AbstractCloseableIteration<E,X extends Exception>

Throws:

X

X extends Exception