content: package org.w3c.dom.traversal;
  
  import org.w3c.dom.Node;
  import org.w3c.dom.DOMException;
  /**
   * <code>TreeWalker</code> objects are used to navigate a document tree or
   * subtree using the view of the document defined by their
   * <code>whatToShow</code> flags and filter (if any). Any function which
   * performs navigation using a <code>TreeWalker</code> will automatically
   * support any view defined by a <code>TreeWalker</code>.
   * <p>Omitting nodes from the logical view of a subtree can result in a
   * structure that is substantially different from the same subtree in the
   * complete, unfiltered document. Nodes that are siblings in the
   * <code>TreeWalker</code> view may be children of different, widely
   * separated nodes in the original view. For instance, consider a
   * <code>NodeFilter</code> that skips all nodes except for Text nodes and
   * the root node of a document. In the logical view that results, all text
   * nodes will be siblings and appear as direct children of the root node, no
   * matter how deeply nested the structure of the original document.
   * <p>See also the <a href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Traversal-Range-20001113'>Document Object Model (DOM) Level 2 Traversal and Range Specification</a>.
   * @since DOM Level 2
   */
  public interface TreeWalker {
      /**
       * The <code>root</code> node of the <code>TreeWalker</code>, as specified
       * when it was created.
       */
      public Node getRoot();
      /**
       * This attribute determines which node types are presented via the
       * <code>TreeWalker</code>. The available set of constants is defined in
       * the <code>NodeFilter</code> interface.  Nodes not accepted by
       * <code>whatToShow</code> will be skipped, but their children may still
       * be considered. Note that this skip takes precedence over the filter,
       * if any.
       */
      public int getWhatToShow();
      /**
       * The filter used to screen nodes.
       */
      public NodeFilter getFilter();
      /**
       * The value of this flag determines whether the children of entity
       * reference nodes are visible to the <code>TreeWalker</code>. If false,
       * these children  and their descendants will be rejected. Note that
       * this rejection takes precedence over <code>whatToShow</code> and the
       * filter, if any.
       * <br> To produce a view of the document that has entity references
       * expanded and does not expose the entity reference node itself, use
       * the <code>whatToShow</code> flags to hide the entity reference node
       * and set <code>expandEntityReferences</code> to true when creating the
       * <code>TreeWalker</code>. To produce a view of the document that has
       * entity reference nodes but no entity expansion, use the
       * <code>whatToShow</code> flags to show the entity reference node and
       * set <code>expandEntityReferences</code> to false.
       */
      public boolean getExpandEntityReferences();
      /**
       * The node at which the <code>TreeWalker</code> is currently positioned.
       * <br>Alterations to the DOM tree may cause the current node to no longer
       * be accepted by the <code>TreeWalker</code>'s associated filter.
       * <code>currentNode</code> may also be explicitly set to any node,
       * whether or not it is within the subtree specified by the
       * <code>root</code> node or would be accepted by the filter and
       * <code>whatToShow</code> flags. Further traversal occurs relative to
       * <code>currentNode</code> even if it is not part of the current view,
       * by applying the filters in the requested direction; if no traversal
       * is possible, <code>currentNode</code> is not changed.
       */
      public Node getCurrentNode();
      /**
       * The node at which the <code>TreeWalker</code> is currently positioned.
       * <br>Alterations to the DOM tree may cause the current node to no longer
       * be accepted by the <code>TreeWalker</code>'s associated filter.
       * <code>currentNode</code> may also be explicitly set to any node,
       * whether or not it is within the subtree specified by the
       * <code>root</code> node or would be accepted by the filter and
       * <code>whatToShow</code> flags. Further traversal occurs relative to
       * <code>currentNode</code> even if it is not part of the current view,
       * by applying the filters in the requested direction; if no traversal
       * is possible, <code>currentNode</code> is not changed.
       * @exception DOMException
       *   NOT_SUPPORTED_ERR: Raised if an attempt is made to set
       *   <code>currentNode</code> to <code>null</code>.
       */
      public void setCurrentNode(Node currentNode)
              throws DOMException;
      /**
       * Moves to and returns the closest visible ancestor node of the current
       * node. If the search for <code>parentNode</code> attempts to step
       * upward from the <code>TreeWalker</code>'s <code>root</code> node, or
       * if it fails to find a visible ancestor node, this method retains the
       * current position and returns <code>null</code>.
       * @return The new parent node, or <code>null</code> if the current node
       *   has no parent  in the <code>TreeWalker</code>'s logical view.
       */
      public Node parentNode();
      /**
       * Moves the <code>TreeWalker</code> to the first visible child of the
       * current node, and returns the new node. If the current node has no
       * visible children, returns <code>null</code>, and retains the current
       * node.
       * @return The new node, or <code>null</code> if the current node has no
       *   visible children  in the <code>TreeWalker</code>'s logical view.
       */
      public Node firstChild();
      /**
       * Moves the <code>TreeWalker</code> to the last visible child of the
       * current node, and returns the new node. If the current node has no
       * visible children, returns <code>null</code>, and retains the current
       * node.
       * @return The new node, or <code>null</code> if the current node has no
       *   children  in the <code>TreeWalker</code>'s logical view.
       */
      public Node lastChild();
      /**
       * Moves the <code>TreeWalker</code> to the previous sibling of the
       * current node, and returns the new node. If the current node has no
       * visible previous sibling, returns <code>null</code>, and retains the
       * current node.
       * @return The new node, or <code>null</code> if the current node has no
       *   previous sibling.  in the <code>TreeWalker</code>'s logical view.
       */
      public Node previousSibling();
      /**
       * Moves the <code>TreeWalker</code> to the next sibling of the current
       * node, and returns the new node. If the current node has no visible
       * next sibling, returns <code>null</code>, and retains the current node.
       * @return The new node, or <code>null</code> if the current node has no
       *   next sibling.  in the <code>TreeWalker</code>'s logical view.
       */
      public Node nextSibling();
      /**
       * Moves the <code>TreeWalker</code> to the previous visible node in
       * document order relative to the current node, and returns the new
       * node. If the current node has no previous node,  or if the search for
       * <code>previousNode</code> attempts to step upward from the
       * <code>TreeWalker</code>'s <code>root</code> node,  returns
       * <code>null</code>, and retains the current node.
       * @return The new node, or <code>null</code> if the current node has no
       *   previous node  in the <code>TreeWalker</code>'s logical view.
       */
      public Node previousNode();
      /**
       * Moves the <code>TreeWalker</code> to the next visible node in document
       * order relative to the current node, and returns the new node. If the
       * current node has no next node, or if the search for nextNode attempts
       * to step upward from the <code>TreeWalker</code>'s <code>root</code>
       * node, returns <code>null</code>, and retains the current node.
       * @return The new node, or <code>null</code> if the current node has no
       *   next node  in the <code>TreeWalker</code>'s logical view.
       */
      public Node nextNode();
  }
  