Package net.sf.saxon.om
Class EmptyIterator
- java.lang.Object
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- net.sf.saxon.om.EmptyIterator
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- All Implemented Interfaces:
LastPositionFinder
,ReversibleIterator
,AxisIterator
,GroundedIterator
,LookaheadIterator
,SequenceIterator
public class EmptyIterator extends java.lang.Object implements AxisIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator
EmptyIterator: an iterator over an empty sequence. Since such an iterator has no state, only one instance is required; therefore a singleton instance is available via the static getInstance() method.
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Field Summary
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Fields inherited from interface net.sf.saxon.om.SequenceIterator
ATOMIZABLE, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
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Constructor Summary
Constructors Constructor Description EmptyIterator()
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description Item
current()
Get the current item, that is, the item returned by the most recent call of next().SequenceIterator
getAnother()
Get another iterator over the same items, positioned at the start.static EmptyIterator
getInstance()
Get an EmptyIterator, an iterator over an empty sequence.int
getLastPosition()
Get the position of the last item in the sequence.int
getProperties()
Get properties of this iterator, as a bit-significant integer.SequenceIterator
getReverseIterator()
Get another iterator over the same items, in reverse order.boolean
hasNext()
Determine whether there are more items to come.Value
materialize()
Return a Value containing all the items in the sequence returned by this SequenceIterator.Item
next()
Get the next item.int
position()
Get the position of the current item.
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Method Detail
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getInstance
public static EmptyIterator getInstance()
Get an EmptyIterator, an iterator over an empty sequence.- Returns:
- an EmptyIterator (in practice, this always returns the same one)
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next
public Item next()
Get the next item. This method should not be called unless hasNext() returns true.- Specified by:
next
in interfaceAxisIterator
- Specified by:
next
in interfaceSequenceIterator
- Returns:
- the next item. For the EmptyIterator this is always null.
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current
public Item current()
Get the current item, that is, the item returned by the most recent call of next().- Specified by:
current
in interfaceAxisIterator
- Specified by:
current
in interfaceSequenceIterator
- Returns:
- the current item. For the EmptyIterator this is always null.
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position
public int position()
Get the position of the current item.- Specified by:
position
in interfaceAxisIterator
- Specified by:
position
in interfaceSequenceIterator
- Returns:
- the position of the current item. For the EmptyIterator this is always zero (whether or not the next() method has been called).
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getLastPosition
public int getLastPosition()
Get the position of the last item in the sequence.- Specified by:
getLastPosition
in interfaceLastPositionFinder
- Returns:
- the position of the last item in the sequence, always zero in this implementation
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getAnother
public SequenceIterator getAnother()
Get another iterator over the same items, positioned at the start.- Specified by:
getAnother
in interfaceAxisIterator
- Specified by:
getAnother
in interfaceSequenceIterator
- Returns:
- another iterator over an empty sequence (in practice, it returns the same iterator each time)
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getReverseIterator
public SequenceIterator getReverseIterator()
Get another iterator over the same items, in reverse order.- Specified by:
getReverseIterator
in interfaceReversibleIterator
- Returns:
- a reverse iterator over an empty sequence (in practice, it returns the same iterator each time)
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getProperties
public int getProperties()
Get properties of this iterator, as a bit-significant integer.- Specified by:
getProperties
in interfaceSequenceIterator
- 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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materialize
public Value materialize()
Return a Value containing all the items in the sequence returned by this SequenceIterator. This should be an "in-memory" value, not a Closure.- Specified by:
materialize
in interfaceGroundedIterator
- Returns:
- the corresponding Value
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hasNext
public boolean hasNext()
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.- Specified by:
hasNext
in interfaceLookaheadIterator
- Returns:
- true if there are more nodes
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