net.sf.saxon.tree.iter

Class EmptyIterator<T extends Item<?>>

java.lang.Object

net.sf.saxon.tree.iter.EmptyIterator<T>

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, AtomizedValueIterator<T>, SequenceIterator<T>, GroundedIterator<T>, LookaheadIterator<T>, ReversibleIterator<T>, UnfailingIterator<T>

Direct Known Subclasses:

EmptyIterator.OfAtomic, EmptyIterator.OfNodes

public class EmptyIterator<T extends Item<?>>
extends java.lang.Object
implements SequenceIterator<T>, ReversibleIterator<T>, LastPositionFinder, GroundedIterator<T>, LookaheadIterator<T>, UnfailingIterator<T>, AtomizedValueIterator<T>

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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	EmptyIterator.OfAtomic An empty iterator for use where a sequence of atomic values is required
static class	EmptyIterator.OfNodes An empty iterator for use where a sequence of nodes is required

Field Summary

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

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	EmptyIterator() Protected constructor

Method Summary

Modifier and Type	Method and Description
static <T extends Item<?>> EmptyIterator<T>	emptyIterator()
static EmptyIterator	getInstance() Get an EmptyIterator, an iterator over an empty sequence.
int	getLength() Get the position of the last item in the sequence.
int	getProperties() Get properties of this iterator, as a bit-significant integer.
GroundedValue<T>	getResidue() Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position.
EmptyIterator<T>	getReverseIterator() Get another iterator over the same items, in reverse order.
boolean	hasNext() Determine whether there are more items to come.
GroundedValue<T>	materialize() Return a Value containing all the items in the sequence returned by this SequenceIterator.
T	next() Get the next item.
AtomicSequence	nextAtomizedValue() Deliver the atomic value that is next in the atomized result

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.tree.iter.UnfailingIterator

firstWith, forEach, toGroundedValue, toList

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

close, forEachOrFail

Constructor Detail

EmptyIterator

protected EmptyIterator()

Protected constructor

Method Detail

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)

emptyIterator

public static <T extends Item<?>> EmptyIterator<T> emptyIterator()

nextAtomizedValue

public AtomicSequence nextAtomizedValue()

Deliver the atomic value that is next in the atomized result

Specified by:

nextAtomizedValue in interface AtomizedValueIterator<T extends Item<?>>

Returns:

the next atomic value

next

public T next()

Get the next item.

Specified by:

next in interface SequenceIterator<T extends Item<?>>

Specified by:

next in interface UnfailingIterator<T extends Item<?>>

Returns:

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

getLength

public int getLength()

Get the position of the last item in the sequence.

Specified by:

getLength in interface LastPositionFinder

Returns:

the position of the last item in the sequence, always zero in this implementation

getReverseIterator

public EmptyIterator<T> getReverseIterator()

Get another iterator over the same items, in reverse order.

Specified by:

getReverseIterator in interface ReversibleIterator<T extends Item<?>>

Returns:

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

getProperties

public int getProperties()

Get properties of this iterator, as a bit-significant integer.

Specified by:

getProperties in interface SequenceIterator<T extends Item<?>>

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.

materialize

public GroundedValue<T> 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 SequenceIterator<T extends Item<?>>

Specified by:

materialize in interface GroundedIterator<T extends Item<?>>

Returns:

the corresponding Value

getResidue

public GroundedValue<T> getResidue()

Description copied from interface: GroundedIterator

Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position. This should be an "in-memory" value, not a Closure. This method does not change the state of the iterator (in particular, it does not consume the iterator).

Specified by:

getResidue in interface GroundedIterator<T extends Item<?>>

Returns:

the corresponding Value

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<T extends Item<?>>

Returns:

true if there are more nodes