Package net.sf.saxon.om
Class SingletonIterator
java.lang.Object
net.sf.saxon.om.SingletonIterator
- All Implemented Interfaces:
LastPositionFinder
,ReversibleIterator
,GroundedIterator
,LookaheadIterator
,SequenceIterator
,UnfailingIterator
public class SingletonIterator
extends Object
implements UnfailingIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator
SingletonIterator: an iterator over a sequence of zero or one values
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Field Summary
Fields inherited from interface net.sf.saxon.om.SequenceIterator
GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
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Method Summary
Modifier and TypeMethodDescriptionvoid
close()
Close the iterator.current()
Get the current item in the sequence.Get another iterator over the same sequence of items, positioned at the start of the sequence.int
Get the last position (that is, the number of items in the sequence).int
Get properties of this iterator, as a bit-significant integer.Get a new SequenceIterator that returns the same items in reverse order.getValue()
boolean
hasNext()
Determine whether there are more items to come.static UnfailingIterator
makeIterator
(Item item) Factory method.Return a Value containing all the items in the sequence returned by this SequenceIteratornext()
Get the next item in the sequence.int
position()
Return the current position in the sequence.
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Method Details
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makeIterator
Factory method.- Parameters:
item
- the item to iterate over- Returns:
- a SingletonIterator over the supplied item, or an EmptyIterator if the supplied item is null.
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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 items
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next
Description copied from interface:UnfailingIterator
Get the next item in the sequence.- Specified by:
next
in interfaceSequenceIterator
- Specified by:
next
in interfaceUnfailingIterator
- Returns:
- the next Item. If there are no more nodes, return null.
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current
Description copied from interface:UnfailingIterator
Get the current item in the sequence.- Specified by:
current
in interfaceSequenceIterator
- Specified by:
current
in interfaceUnfailingIterator
- Returns:
- the current item, that is, the item most recently returned by next()
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position
public int position()Return the current position in the sequence.- Specified by:
position
in interfaceSequenceIterator
- Specified by:
position
in interfaceUnfailingIterator
- Returns:
- 0 before the first call on next(); 1 before the second call on next(); -1 after the second call on next().
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getLastPosition
public int getLastPosition()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:
getLastPosition
in interfaceLastPositionFinder
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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
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getAnother
Description copied from interface:UnfailingIterator
Get another iterator over the same sequence of items, positioned at the start of the sequence. It must be possible to call this method at any time, whether none, some, or all of the items in the original iterator have been read. The method is non-destructive: it does not change the state of the original iterator.- Specified by:
getAnother
in interfaceSequenceIterator
- Specified by:
getAnother
in interfaceUnfailingIterator
- Returns:
- a new iterator over the same sequence
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getReverseIterator
Description copied from interface:ReversibleIterator
Get a new SequenceIterator that returns the same items in reverse order. If this SequenceIterator is an AxisIterator, then the returned SequenceIterator must also be an AxisIterator.- Specified by:
getReverseIterator
in interfaceReversibleIterator
- Returns:
- an iterator over the items in reverse order
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getValue
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materialize
Return a Value containing all the items in the sequence returned by this SequenceIterator- Specified by:
materialize
in interfaceGroundedIterator
- Returns:
- the corresponding Value. If the value is a closure or a function call package, it will be evaluated and expanded.
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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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