net.sf.saxon.om
Class SingleNodeIterator

java.lang.Object
  extended by net.sf.saxon.om.SingleNodeIterator
All Implemented Interfaces:
LastPositionFinder, ReversibleIterator, AxisIterator, GroundedIterator, LookaheadIterator, SequenceIterator, UnfailingIterator

public class SingleNodeIterator
extends Object
implements AxisIterator, UnfailingIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator

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


Field Summary
 
Fields inherited from interface net.sf.saxon.om.SequenceIterator
GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
 
Method Summary
 Value atomize()
          Return the atomized value of the current node.
 Item current()
          Get the current value in the sequence (the one returned by the most recent call on next()).
 SequenceIterator getAnother()
          Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
 int getLastPosition()
          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.
 SequenceIterator getReverseIterator()
          Get a new SequenceIterator that returns the same items in reverse order.
 CharSequence getStringValue()
          Return the string value of the current node.
 Item getValue()
           
 boolean hasNext()
          Determine whether there are more items to come.
 AxisIterator iterateAxis(byte axis, NodeTest test)
          Return an iterator over an axis, starting at the current node.
static AxisIterator makeIterator(NodeInfo item)
          Factory method.
 GroundedValue materialize()
          Return a Value containing all the items in the sequence returned by this SequenceIterator
 boolean moveNext()
          Move to the next node, without returning it.
 Item next()
          Get the next item in the sequence.
 int position()
          Return the current position in the sequence.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

makeIterator

public static AxisIterator makeIterator(NodeInfo 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.

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

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.

Specified by:
moveNext in interface AxisIterator

next

public Item next()
Description copied from interface: SequenceIterator
Get the next item in the sequence. This method changes the state of the iterator, in particular it affects the result of subsequent calls of position() and current().

Specified by:
next in interface SequenceIterator
Specified by:
next in interface UnfailingIterator
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.

current

public Item current()
Description copied from interface: SequenceIterator
Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next(). This method does not change the state of the iterator.

Specified by:
current in interface SequenceIterator
Specified by:
current in interface UnfailingIterator
Returns:
the current item, the one most recently returned by a call on next(). Returns null if next() has not been called, or if the end of the sequence has been reached.

position

public int position()
Return the current position in the sequence.

Specified by:
position in interface SequenceIterator
Specified by:
position in interface UnfailingIterator
Returns:
0 before the first call on next(); 1 before the second call on next(); -1 after the second call on next().

getLastPosition

public int getLastPosition()
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:
getLastPosition in interface LastPositionFinder

iterateAxis

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

Specified by:
iterateAxis in interface AxisIterator
Parameters:
axis - the axis to iterate over, using a constant such as Axis.CHILD
test - a predicate to apply to the nodes before returning them.

atomize

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

Specified by:
atomize in interface AxisIterator
Returns:
the atomized value.
Throws:
NullPointerException - if there is no current node
XPathException

getStringValue

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

Specified by:
getStringValue in interface AxisIterator
Returns:
the string value, as an instance of CharSequence.
Throws:
NullPointerException - if there is no current node

getAnother

public SequenceIterator getAnother()
Description copied from interface: SequenceIterator
Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.

This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.

This method does not change the state of the iterator.

Specified by:
getAnother in interface SequenceIterator
Specified by:
getAnother in interface UnfailingIterator
Returns:
a SequenceIterator that iterates over the same items, positioned before the first item

getReverseIterator

public SequenceIterator 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.

getProperties

public int getProperties()
Get properties of this iterator, as a bit-significant integer.

Specified by:
getProperties in interface SequenceIterator
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.


Copyright (C) Michael H. Kay. All rights reserved.