net.sf.saxon.om
Class SingletonIterator

java.lang.Object
  net.sf.saxon.om.SingletonIterator

All Implemented Interfaces:

AtomizableIterator, AxisIterator, GroundedIterator, LastPositionFinder, LookaheadIterator, ReversibleIterator, SequenceIterator

public class SingletonIterator

extends java.lang.Object

implements AxisIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator, AtomizableIterator

SingletonIterator: an iterator over a sequence of zero or one values

Field Summary

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

ATOMIZABLE, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Method Summary

Item	current() Get the current item in the sequence.
SequenceIterator	getAnother() Get another iterator over the same sequence of items, positioned at the start of the sequence.
int	getLastPosition() 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.
SequenceIterator	getReverseIterator() Get a new SequenceIterator that returns the same items in reverse order.
Item	getValue()
boolean	hasNext() Determine whether there are more items to come.
static AxisIterator	makeIterator(Item item) Factory method.
Value	materialize() Return a SequenceExtent containing all the items in the sequence returned by this SequenceIterator
Item	next() Get the next item in the sequence.
int	position() Return the current position in the sequence.
void	setIsAtomizing(boolean atomizing) Indicate that any nodes returned in the sequence will be atomized.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

makeIterator

public static AxisIterator makeIterator(Item item)

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.

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 items

next

public Item next()

Description copied from interface: AxisIterator

Get the next item in the sequence.

Specified by:

next in interface AxisIterator

Returns:

the next Item. If there are no more nodes, return null.

current

public Item current()

Description copied from interface: AxisIterator

Get the current item in the sequence.

Specified by:

current in interface AxisIterator

Returns:

the current item, that is, the item most recently returned by next()

position

public int position()

Return the current position in the sequence.

Specified by:

position in interface AxisIterator

Returns:

0 before the first call on next(); 1 before the second call on next(); -1 after the second call on next().

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 setting SequenceIterator.LAST_POSITION_FINDER

Specified by:

getLastPosition in interface LastPositionFinder

getAnother

public SequenceIterator getAnother()

Description copied from interface: AxisIterator

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 interface AxisIterator

Returns:

a new iterator over the same sequence

getReverseIterator

public SequenceIterator 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 interface ReversibleIterator

getValue

public Item getValue()

materialize

public Value materialize()

Return a SequenceExtent containing all the items in the sequence returned by this SequenceIterator

Specified by:

materialize in interface GroundedIterator

Returns:

the corresponding SequenceExtent if it exists, or null if it doesn't; in this case the caller must construct a new SequenceExtent by calling new SequenceExtent(iter.getAnother())

setIsAtomizing

public void setIsAtomizing(boolean atomizing)

Indicate that any nodes returned in the sequence will be atomized. This means that if it wishes to do so, the implementation can return the typed values of the nodes rather than the nodes themselves. The implementation is free to ignore this hint.

This implementation attempts atomization of a singleton node if it is untyped. This avoids adding an iterator to iterate over the value in the common case where the typed value of the node is a single atomic value.

Specified by:

setIsAtomizing in interface AtomizableIterator

Parameters:

atomizing - true if the caller of this iterator will atomize any nodes that are returned, and is therefore willing to accept the typed value of the nodes instead of the nodes themselves.

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 GROUNDED, LAST_POSITION_FINDER, and 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.