org.jaxen.util
Class PrecedingAxisIterator

java.lang.Object
  extended by org.jaxen.util.PrecedingAxisIterator
All Implemented Interfaces:
Iterator

public class PrecedingAxisIterator
extends Object
implements Iterator

Represents the XPath preceding axis. The "preceding axis contains all nodes in the same document as the context node that are before the context node in document order, excluding any ancestors and excluding attribute nodes and namespace nodes."

This implementation of 'preceding' works like so: the preceding axis includes preceding siblings of this node and their descendants. Also, for each ancestor node of this node, it includes all preceding siblings of that ancestor, and their descendants. Finally, it includes the ancestor nodes themselves.

The reversed descendant-or-self axes that are required are calculated using a stack of reversed 'child-or-self' axes. When asked for a node, it is always taken from a child-or-self axis. If it was the last node on that axis, the node is returned. Otherwise, this axis is pushed on the stack, and the process is repeated with the child-or-self of the node. Eventually this recurses down to the last descendant of any node, then works back up to the root.

Most object models could provide a faster implementation of the reversed 'children-or-self' used here.

Version:
1.2b12

Constructor Summary
PrecedingAxisIterator(Object contextNode, Navigator navigator)
          Create a new preceding axis iterator.
 
Method Summary
 boolean hasNext()
          Returns true if there are any preceding nodes remaining; false otherwise.
 Object next()
          Returns the next preceding node.
 void remove()
          This operation is not supported.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PrecedingAxisIterator

public PrecedingAxisIterator(Object contextNode,
                             Navigator navigator)
                      throws UnsupportedAxisException
Create a new preceding axis iterator.

Parameters:
contextNode - the node to start from
navigator - the object model specific navigator
Throws:
UnsupportedAxisException
Method Detail

hasNext

public boolean hasNext()
Returns true if there are any preceding nodes remaining; false otherwise.

Specified by:
hasNext in interface Iterator
Returns:
true if any preceding nodes remain; false otherwise
See Also:
Iterator.hasNext()

next

public Object next()
            throws NoSuchElementException
Returns the next preceding node.

Specified by:
next in interface Iterator
Returns:
the next preceding node
Throws:
NoSuchElementException - if no preceding nodes remain
See Also:
Iterator.next()

remove

public void remove()
            throws UnsupportedOperationException
This operation is not supported.

Specified by:
remove in interface Iterator
Throws:
UnsupportedOperationException - always


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