net.sf.saxon.tree.iter

Class SingletonIterator

java.lang.Object

net.sf.saxon.tree.iter.SingletonIterator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, SequenceIterator, GroundedIterator, LookaheadIterator, ReversibleIterator

Direct Known Subclasses:

SingleAtomicIterator

public class SingletonIterator
extends java.lang.Object
implements SequenceIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator

SingletonIterator: an iterator over a sequence of exactly one item

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SingletonIterator(Item value) Private constructor: external classes should use the factory method

Method Summary

Modifier and Type	Method and Description
int	getLength() Get the last position (that is, the number of items in the sequence).
GroundedValue	getResidue() Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position.
SingletonIterator	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.
boolean	isActuallyGrounded() Ask if the iterator is actually grounded.
static SequenceIterator	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.
boolean	supportsGetLength() Ask whether this iterator supports use of the LastPositionFinder.getLength() method.
boolean	supportsHasNext() Ask whether the hasNext() method can be called.

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.om.SequenceIterator

close, discharge

Constructor Detail

SingletonIterator

protected SingletonIterator(Item value)

Private constructor: external classes should use the factory method

Parameters:

value - the item to iterate over

Method Detail

makeIterator

public static SequenceIterator 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.

supportsHasNext

public boolean supportsHasNext()

Description copied from interface: LookaheadIterator

Ask whether the hasNext() method can be called. This method must be called before calling hasNext(), because some iterators implement this interface, but only support look-ahead under particular circumstances (this is usually because they delegate to another iterator)

Specified by:

supportsHasNext in interface LookaheadIterator

Returns:

true if the LookaheadIterator.hasNext() method is available

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: SequenceIterator

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

Specified by:

next in interface SequenceIterator

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.

supportsGetLength

public boolean supportsGetLength()

Description copied from interface: LastPositionFinder

Ask whether this iterator supports use of the LastPositionFinder.getLength() method. This method should always be called before calling LastPositionFinder.getLength(), because an iterator that implements this interface may support use of LastPositionFinder.getLength() in some situations and not in others

Specified by:

supportsGetLength in interface LastPositionFinder

Returns:

true if the LastPositionFinder.getLength() method can be called to determine the length of the underlying sequence.

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 LastPositionFinder.supportsGetLength() has been called and has returned true.

Specified by:

getLength in interface LastPositionFinder

Returns:

the number of items in the sequence

isActuallyGrounded

public boolean isActuallyGrounded()

Description copied from interface: GroundedIterator

Ask if the iterator is actually grounded. This method must be called before calling GroundedIterator.materialize() or GroundedIterator.getResidue(), because the iterator might be grounded under some conditions and not others (usually when it delegates to another iterator)

Specified by:

isActuallyGrounded in interface GroundedIterator

Returns:

true if this iterator is grounded

getReverseIterator

public SingletonIterator 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.

getResidue

public GroundedValue 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

Returns:

the corresponding Value