net.sf.saxon.om

Interface FocusIterator

All Superinterfaces:

SequenceIterator

All Known Implementing Classes:

FocusTrackingIterator, GroupByIterator.ManualGroupByIterator, ManualGroupIterator, ManualIterator, MergeGroupingIterator.ManualMergeGroupingIterator

public interface FocusIterator
extends SequenceIterator

An iterator that maintains the values of position() and current(), typically implemented as a wrapper over an iterator which does not maintain these values itself.

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Method Summary

Methods

Modifier and Type	Method and Description
Item	current() Get the current value in the sequence (the one returned by the most recent call on next()).
FocusIterator	getAnother() Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
int	getLength() Get the position of the last item in the sequence
int	position() Get the current position.

Methods inherited from interface net.sf.saxon.om.SequenceIterator

close, getProperties, next

Method Detail

current

Item current()

Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next(). This method does not change the state of the iterator.

Returns:

the current item, the one most recently returned by a call on next(). Returns null if next() has not been called, or if the end of the sequence has been reached.

Since:

8.4

position

int position()

Get the current position. This will usually be zero before the first call on next(), otherwise it will be the number of times that next() has been called. Once next() has returned null, the preferred action is for subsequent calls on position() to return -1, but not all existing implementations follow this practice. (In particular, the EmptyIterator is stateless, and always returns 0 as the value of position(), whether or not next() has been called.)

This method does not change the state of the iterator.

Returns:

the current position, the position of the item returned by the most recent call of next(). This is 1 after next() has been successfully called once, 2 after it has been called twice, and so on. If next() has never been called, the method returns zero. If the end of the sequence has been reached, the value returned will always be <= 0; the preferred value is -1.

Since:

8.4

getLength

int getLength()
              throws XPathException

Get the position of the last item in the sequence

Returns:

the position of the last item

Throws:

XPathException - if a failure occurs reading the sequence

getAnother

FocusIterator getAnother()
                         throws XPathException

Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.

This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.

This method does not change the state of the iterator.

Some implementations of this method may regenerate the input sequence, creating new nodes with different identity from the original. This is not recommended, but is hard to prevent. This causes no problem for the primary usage of this method to support the last() function, but it has been known to cause trouble in other situations.

Specified by:

getAnother in interface SequenceIterator

Returns:

a SequenceIterator that iterates over the same items, positioned before the first item

Throws:

XPathException - if any error occurs

Since:

8.4