net.sf.saxon.om
Class Navigator.BaseEnumeration

java.lang.Object
  net.sf.saxon.om.AxisIteratorImpl
      net.sf.saxon.om.Navigator.BaseEnumeration

All Implemented Interfaces:

AxisIterator, SequenceIterator, UnfailingIterator

Direct Known Subclasses:

Navigator.AncestorEnumeration, Navigator.DescendantEnumeration, Navigator.FollowingEnumeration, Navigator.PrecedingEnumeration

Enclosing class:

Navigator

public abstract static class Navigator.BaseEnumeration
extends AxisIteratorImpl

BaseEnumeration is an abstract implementation of an AxisIterator, it simplifies the implementation of the underlying AxisIterator by requiring it to provide only two methods: advance(), and getAnother().

NOTA BENE: BaseEnumeration does not maintain the value of the position variable. It must therefore either (a) be wrapped in an AxisFilter, which does maintain position, or (b) be subclassed by a class that maintains position itself.

Field Summary

Fields inherited from class net.sf.saxon.om.AxisIteratorImpl

current, position

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Navigator.BaseEnumeration()

Method Summary

abstract void	advance() The advance() method must be provided in each concrete implementation.
abstract SequenceIterator	getAnother() Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
Item	next() Get the next item in the sequence.

Methods inherited from class net.sf.saxon.om.AxisIteratorImpl

atomize, close, current, getProperties, getStringValue, iterateAxis, moveNext, position

Methods inherited from class java.lang.Object

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

Constructor Detail

Navigator.BaseEnumeration

public Navigator.BaseEnumeration()

Method Detail

next

public final 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().

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.

advance

public abstract void advance()

The advance() method must be provided in each concrete implementation. It must leave the variable current set to the next node to be returned in the iteration, or to null if there are no more nodes to be returned.

getAnother

public abstract 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.

Returns:

a SequenceIterator that iterates over the same items, positioned before the first item