net.sf.saxon.om

Class EmptyIterator

Implemented Interfaces:
AxisIterator, GroundedIterator, LastPositionFinder, LookaheadIterator, ReversibleIterator, SequenceIterator, UnfailingIterator

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.

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Method Summary

Value
atomize()
Return the atomized value of the current node.
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.
CharSequence
getStringValue()
Return the string value of the current node.
boolean
hasNext()
Determine whether there are more items to come.
AxisIterator
iterateAxis(byte axis, NodeTest test)
Return an iterator over an axis, starting at the current node.
GroundedValue
materialize()
Return a Value containing all the items in the sequence returned by this SequenceIterator.
boolean
moveNext()
Move to the next node, without returning it.
Item
next()
Get the next item.
int
position()
Get the position of the current item.

Method Details

atomize

public Value atomize()
            throws XPathException
Return the atomized value of the current node.
Specified by:
atomize in interface AxisIterator
Returns:
the atomized value.

current

public Item current()
Get the current item, that is, the item returned by the most recent call of next().
Specified by:
current in interface UnfailingIterator
current in interface SequenceIterator
Returns:
the current item. For the EmptyIterator this is always null.

getAnother

public SequenceIterator getAnother()
Get another iterator over the same items, positioned at the start.
Specified by:
getAnother in interface UnfailingIterator
getAnother in interface SequenceIterator
Returns:
another iterator over an empty sequence (in practice, it returns the same iterator each time)

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)

getLastPosition

public int getLastPosition()
Get the position of the last item in the sequence.
Specified by:
getLastPosition in interface LastPositionFinder
Returns:
the position of the last item in the sequence, always zero in this implementation

getProperties

public int getProperties()
Get properties of this iterator, as a bit-significant integer.
Specified by:
getProperties in interface SequenceIterator
Returns:
the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.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.

getReverseIterator

public SequenceIterator getReverseIterator()
Get another iterator over the same items, in reverse order.
Specified by:
getReverseIterator in interface ReversibleIterator
Returns:
a reverse iterator over an empty sequence (in practice, it returns the same iterator each time)

getStringValue

public CharSequence getStringValue()
Return the string value of the current node.
Specified by:
getStringValue in interface AxisIterator
Returns:
the string value, as an instance of CharSequence.

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 interface LookaheadIterator
Returns:
true if there are more nodes

iterateAxis

public AxisIterator iterateAxis(byte axis,
                                NodeTest test)
Return an iterator over an axis, starting at the current node.
Specified by:
iterateAxis in interface AxisIterator
Parameters:
axis - the axis to iterate over, using a constant such as Axis.CHILD
test - a predicate to apply to the nodes before returning them.

materialize

public GroundedValue 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 interface GroundedIterator
Returns:
the corresponding Value

moveNext

public boolean moveNext()
Move to the next node, without returning it. Returns true if there is a next node, false if the end of the sequence has been reached. After calling this method, the current node may be retrieved using the current() function.
Specified by:
moveNext in interface AxisIterator

next

public Item next()
Get the next item.
Specified by:
next in interface UnfailingIterator
next in interface SequenceIterator
Returns:
the next item. For the EmptyIterator this is always null.

position

public int position()
Get the position of the current item.
Specified by:
position in interface UnfailingIterator
position in interface SequenceIterator
Returns:
the position of the current item. For the EmptyIterator this is always zero (whether or not the next() method has been called).