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
Valueatomize()
Return the atomized value of the current node.
voidclose()
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.
CharSequencegetStringValue()
Return the string value of the current node.
booleanhasNext()
Determine whether there are more items to come.
AxisIteratoriterateAxis(byte axis, NodeTest test)
Return an iterator over an axis, starting at the current node.
GroundedValuematerialize()
Return a Value containing all the items in the sequence returned by this SequenceIterator.
booleanmoveNext()
Move to the next node, without returning it.
Itemnext()
Get the next item.
intposition()
Get the position of the current item.

Method Detail

atomize

public Value atomize()
Return the atomized value of the current node.

Returns: the atomized value.

Throws: NullPointerException if there is no current node

close

public void close()

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 EmptyIterator, EmptyIterator, and EmptyIterator. 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)

getStringValue

public CharSequence getStringValue()
Return the string value of the current node.

Returns: the string value, as an instance of CharSequence.

Throws: NullPointerException if there is no current node

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

iterateAxis

public AxisIterator iterateAxis(byte axis, NodeTest test)
Return an iterator over an axis, starting at the current node.

Parameters: axis the axis to iterate over, using a constant such as CHILD test a predicate to apply to the nodes before returning them.

Throws: NullPointerException if there is no current node

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.

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.

next

public Item next()
Get the next item.

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).