Package org.eclipse.rdf4j.query.algebra.evaluation.iterator

Class PeekMarkIterator<E>

java.lang.Object

org.eclipse.rdf4j.query.algebra.evaluation.iterator.PeekMarkIterator<E>

All Implemented Interfaces:

AutoCloseable, Iterator<E>, CloseableIteration<E>

@Experimental
public class PeekMarkIterator<E>
extends Object
implements CloseableIteration<E>

An iterator that allows to peek at the next element without consuming it. It also allows to mark the current position and reset to that position.

Author:

Håvard M. Ottestad

Constructor Summary

Constructors

Constructor	Description
PeekMarkIterator(CloseableIteration<E> iterator)

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this iteration, freeing any resources that it is holding.
boolean	hasNext()
void	mark()	Mark the current position so that the iterator can be reset to the current state.
E	next()
E	peek()
void	reset()	Reset the iterator to the marked position.
void	unmark()	Unmark the iterator.

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, remove

Constructor Details

PeekMarkIterator

public PeekMarkIterator(CloseableIteration<E> iterator)

Method Details

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<E>

next

public E next()

Specified by:

next in interface Iterator<E>

peek

public E peek()

Returns:

the next element without consuming it, or null if there are no more elements

mark

public void mark()

Mark the current position so that the iterator can be reset to the current state. This will cause elements to be stored in memory until one of reset(), unmark() or mark() is called.

reset

public void reset()

Reset the iterator to the marked position. Resetting an iterator multiple times will always reset to the same position. Resetting an iterator turns off marking. If the iterator was reset previously and the iterator has advanced beyond the point where reset was initially called, then the iterator can no longer be reset because there will be elements that were not stored while the iterator was marked and resetting will cause these elements to be lost.

close

public void close()

Description copied from interface: CloseableIteration

Closes this iteration, freeing any resources that it is holding. If the iteration has already been closed then invoking this method has no effect.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface CloseableIteration<E>

unmark

public void unmark()

Unmark the iterator. This will cause the iterator to stop buffering elements. If the iterator was recently reset and there are still elements in the buffer, then these elements will still be returned by next().