Package net.sf.saxon.tree.iter
Class UntypedAtomizingIterator<B extends Item>
- java.lang.Object
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- net.sf.saxon.tree.iter.UntypedAtomizingIterator<B>
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- All Implemented Interfaces:
LastPositionFinder<AtomicValue>
,SequenceIterator<AtomicValue>
,LookaheadIterator<AtomicValue>
public class UntypedAtomizingIterator<B extends Item> extends java.lang.Object implements SequenceIterator<AtomicValue>, LastPositionFinder<AtomicValue>, LookaheadIterator<AtomicValue>
AtomizingIterator returns the atomization of an underlying sequence supplied as an iterator. We use a specialist class rather than a general-purpose MappingIterator for performance, especially as the relationship of items in the result sequence to those in the base sequence is often one-to-one. This UntypedAtomizingIterator is used only when it is known that all nodes will be untyped, and that atomizing a node therefore always returns a singleton. However, it is not necessarily the case that the input sequence contains only nodes, and therefore the result sequence may contains atomic values that are not untyped. The parameter type B denotes the type of the items being atomized.
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Field Summary
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Fields inherited from interface net.sf.saxon.om.SequenceIterator
GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
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Constructor Summary
Constructors Constructor Description UntypedAtomizingIterator(SequenceIterator<B> base)
Construct an AtomizingIterator that will atomize the values returned by the base iterator.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Close the iterator.AtomicValue
current()
Get the current value in the sequence (the one returned by the most recent call on next()).SequenceIterator<AtomicValue>
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 last position (that is, the number of items in the sequence).int
getProperties()
Get properties of this iterator, as a bit-significant integer.boolean
hasNext()
Determine whether there are more items to come.AtomicValue
next()
Get the next item in the sequence.int
position()
Get the current position.
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Constructor Detail
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UntypedAtomizingIterator
public UntypedAtomizingIterator(SequenceIterator<B> base)
Construct an AtomizingIterator that will atomize the values returned by the base iterator.- Parameters:
base
- the base iterator
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Method Detail
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next
public AtomicValue next() throws XPathException
Description copied from interface:SequenceIterator
Get the next item in the sequence. This method changes the state of the iterator, in particular it affects the result of subsequent calls of position() and current().- Specified by:
next
in interfaceSequenceIterator<B extends Item>
- Returns:
- the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.
- Throws:
XPathException
- if an error occurs retrieving the next item
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current
public AtomicValue current()
Description copied from interface:SequenceIterator
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.- Specified by:
current
in interfaceSequenceIterator<B extends Item>
- 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.
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position
public int position()
Description copied from interface:SequenceIterator
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.
- Specified by:
position
in interfaceSequenceIterator<B extends Item>
- 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.
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close
public void close()
Description copied from interface:SequenceIterator
Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.(Currently, closing an iterator is important only when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.)
- Specified by:
close
in interfaceSequenceIterator<B extends Item>
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getAnother
public SequenceIterator<AtomicValue> getAnother() throws XPathException
Description copied from interface:SequenceIterator
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.
- Specified by:
getAnother
in interfaceSequenceIterator<B extends Item>
- Returns:
- a SequenceIterator that iterates over the same items, positioned before the first item
- Throws:
XPathException
- if any error occurs
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getProperties
public int getProperties()
Get properties of this iterator, as a bit-significant integer.- Specified by:
getProperties
in interfaceSequenceIterator<B extends Item>
- Returns:
- the properties of this iterator. This will be some combination of
properties such as
SequenceIterator.GROUNDED
,SequenceIterator.LAST_POSITION_FINDER
, andSequenceIterator.LOOKAHEAD
. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.
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getLength
public int getLength() throws XPathException
Description copied from interface:LastPositionFinder
Get the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the result of getProperties() on the iterator includes the bit settingSequenceIterator.LAST_POSITION_FINDER
- Specified by:
getLength
in interfaceLastPositionFinder<B extends Item>
- Returns:
- the number of items in the sequence
- Throws:
XPathException
- if an error occurs evaluating the sequence in order to determine the number of items
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hasNext
public boolean hasNext()
Description copied from interface:LookaheadIterator
Determine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element. This method must not be called unless the result of getProperties() on the iterator includes the bit settingSequenceIterator.LOOKAHEAD
- Specified by:
hasNext
in interfaceLookaheadIterator<B extends Item>
- Returns:
- true if there are more items in the sequence
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