net.sf.saxon.om

Class EmptyIterator

public class EmptyIterator extends 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.
Method Summary
Itemcurrent()
Get the current item, that is, the item returned by the most recent call of next().
SequenceIteratorgetAnother()
Get another iterator over the same items, positioned at the start.
static EmptyIteratorgetInstance()
Get an EmptyIterator, an iterator over an empty sequence.
intgetLastPosition()
Get the position of the last item in the sequence.
intgetProperties()
Get properties of this iterator, as a bit-significant integer.
SequenceIteratorgetReverseIterator()
Get another iterator over the same items, in reverse order.
booleanhasNext()
Determine whether there are more items to come.
Valuematerialize()
Return a Value containing all the items in the sequence returned by this SequenceIterator.
Itemnext()
Get the next item.
intposition()
Get the position of the current item.

Method Detail

current

public Item current()
Get the current item, that is, the item returned by the most recent call of next().

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.

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.

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.

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.

getReverseIterator

public SequenceIterator getReverseIterator()
Get another iterator over the same items, in reverse order.

Returns: a reverse iterator over an empty sequence (in practice, it returns the same iterator each time)

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.

Returns: true if there are more nodes

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.

Returns: the corresponding Value

next

public Item next()
Get the next item. This method should not be called unless hasNext() returns true.

Returns: the next item. For the EmptyIterator this is always null.

position

public int position()
Get the position of the current item.

Returns: the position of the current item. For the EmptyIterator this is always zero (whether or not the next() method has been called).