net.sf.saxon.om
Class Navigator.BaseEnumeration

java.lang.Object
  extended by net.sf.saxon.om.AxisIteratorImpl
      extended by 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 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, current, getProperties, getStringValue, iterateAxis, moveNext, position
 
Methods inherited from class java.lang.Object
equals, 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


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