net.sf.saxon.tree.iter
Class SingletonIterator

java.lang.Object
  net.sf.saxon.tree.iter.SingletonIterator

All Implemented Interfaces:

LastPositionFinder, SequenceIterator, GroundedIterator, LookaheadIterator, ReversibleIterator, UnfailingIterator

public class SingletonIterator
extends Object
implements UnfailingIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator

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

Field Summary

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Method Summary

void	close() Close the iterator.
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 UnfailingIterator	makeIterator(Item item) Factory method.
GroundedValue	materialize() Return a Value 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.

Methods inherited from class java.lang.Object

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

Method Detail

makeIterator

public static UnfailingIterator 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: UnfailingIterator

Get the next item in the sequence.

Specified by:

next in interface SequenceIterator

Specified by:

next in interface UnfailingIterator

Returns:

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

current

public Item current()

Description copied from interface: UnfailingIterator

Get the current item in the sequence.

Specified by:

current in interface SequenceIterator

Specified by:

current in interface UnfailingIterator

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 SequenceIterator

Specified by:

position in interface UnfailingIterator

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

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 interface SequenceIterator

getAnother

public SequenceIterator 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 interface SequenceIterator

Specified by:

getAnother in interface UnfailingIterator

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

Returns:

an iterator over the items in reverse order

getValue

public Item getValue()

materialize

public GroundedValue materialize()

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

Specified by:

materialize in interface GroundedIterator

Returns:

the corresponding Value. If the value is a closure or a function call package, it will be evaluated and expanded.

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.