net.sf.saxon.tree.iter

Class SingletonIterator<T extends Item<?>>

java.lang.Object

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

All Implemented Interfaces:

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

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

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

Field Summary

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

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Method Summary

Modifier and Type	Method and Description
void	close() Close the iterator.
void	forEach(java.util.function.Consumer<T> consumer)
void	forEachOrFail(ItemConsumer<T> consumer) Process all the remaining items delivered by the SequenceIterator using a supplied consumer function.
int	getLength() 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.
GroundedValue<T>	getResidue() Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position.
SingletonIterator<T>	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 <T extends Item<?>> UnfailingIterator<T>	makeIterator(T item) Factory method.
GroundedValue<T>	materialize() Return a Value containing all the items in the sequence returned by this SequenceIterator
T	next() Get the next item in the sequence.
static <T extends Item<?>> SingletonIterator<T>	rawIterator(T item) Factory method for use when it is known the item will not be null

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, toGroundedValue, toList

Method Detail

makeIterator

public static <T extends Item<?>> UnfailingIterator<T> makeIterator(T 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.

rawIterator

public static <T extends Item<?>> SingletonIterator<T> rawIterator(T item)

Factory method for use when it is known the item will not be null

Parameters:

item - the item to iterate over; must not be null

Returns:

a SingletonIterator over the supplied item

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 items

next

public T next()

Description copied from interface: SequenceIterator

Get the next item in the sequence. This method changes the state of the iterator.

Specified by:

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

Specified by:

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

Returns:

the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.

getLength

public int getLength()

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:

getLength in interface LastPositionFinder

Returns:

the number of items in the sequence

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.

For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

Closing an iterator is important 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 java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

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

getReverseIterator

public SingletonIterator<T> 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<T extends Item<?>>

Returns:

an iterator over the items in reverse order

getValue

public Item getValue()

materialize

public GroundedValue<T> materialize()

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

Specified by:

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

Specified by:

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

Returns:

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

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

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.

forEach

public void forEach(java.util.function.Consumer<T> consumer)

Specified by:

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

forEachOrFail

public void forEachOrFail(ItemConsumer<T> consumer)
                   throws XPathException

Description copied from interface: SequenceIterator

Process all the remaining items delivered by the SequenceIterator using a supplied consumer function.

Specified by:

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

Parameters:

consumer - the supplied consumer function

Throws:

XPathException - if either (a) an error occurs obtaining an item from the input sequence, or (b) the consumer throws an exception.