Java Module java.xml Package org.w3c.dom.traversal Interface TreeWalker（JDK11）

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```
public interface TreeWalker
```
TreeWalker objects are used to navigate a document tree or subtree using the view of the document defined by their whatToShow flags and filter (if any). Any function which performs navigation using a TreeWalker will automatically support any view defined by a TreeWalker.
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 TreeWalker view may be children of different, widely separated nodes in the original view. For instance, consider a NodeFilter 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.

See also the Document Object Model (DOM) Level 2 Traversal and Range Specification.

Since:

9, DOM Level 2

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`Node`	`firstChild()`	Moves the `TreeWalker` to the first visible child of the current node, and returns the new node.
`Node`	`getCurrentNode()`	The node at which the `TreeWalker` is currently positioned.
`boolean`	`getExpandEntityReferences()`	The value of this flag determines whether the children of entity reference nodes are visible to the `TreeWalker`.
`NodeFilter`	`getFilter()`	The filter used to screen nodes.
`Node`	`getRoot()`	The `root` node of the `TreeWalker`, as specified when it was created.
`int`	`getWhatToShow()`	This attribute determines which node types are presented via the `TreeWalker`.
`Node`	`lastChild()`	Moves the `TreeWalker` to the last visible child of the current node, and returns the new node.
`Node`	`nextNode()`	Moves the `TreeWalker` to the next visible node in document order relative to the current node, and returns the new node.
`Node`	`nextSibling()`	Moves the `TreeWalker` to the next sibling of the current node, and returns the new node.
`Node`	`parentNode()`	Moves to and returns the closest visible ancestor node of the current node.
`Node`	`previousNode()`	Moves the `TreeWalker` to the previous visible node in document order relative to the current node, and returns the new node.
`Node`	`previousSibling()`	Moves the `TreeWalker` to the previous sibling of the current node, and returns the new node.
`void`	`setCurrentNode(Node currentNode)`	The node at which the `TreeWalker` is currently positioned.

- Method Detail
  - getRoot
```
Node getRoot()
```
    The root node of the TreeWalker, as specified when it was created.
  - getWhatToShow
```
int getWhatToShow()
```
    This attribute determines which node types are presented via the TreeWalker. The available set of constants is defined in the NodeFilter interface. Nodes not accepted by whatToShow will be skipped, but their children may still be considered. Note that this skip takes precedence over the filter, if any.
  - getFilter
```
NodeFilter getFilter()
```
    The filter used to screen nodes.
  - getExpandEntityReferences
```
boolean getExpandEntityReferences()
```
    The value of this flag determines whether the children of entity reference nodes are visible to the TreeWalker. If false, these children and their descendants will be rejected. Note that this rejection takes precedence over whatToShow and the filter, if any.
    To produce a view of the document that has entity references expanded and does not expose the entity reference node itself, use the whatToShow flags to hide the entity reference node and set expandEntityReferences to true when creating the TreeWalker. To produce a view of the document that has entity reference nodes but no entity expansion, use the whatToShow flags to show the entity reference node and set expandEntityReferences to false.
  - getCurrentNode
```
Node getCurrentNode()
```
    The node at which the TreeWalker is currently positioned.
    Alterations to the DOM tree may cause the current node to no longer be accepted by the TreeWalker's associated filter. currentNode may also be explicitly set to any node, whether or not it is within the subtree specified by the root node or would be accepted by the filter and whatToShow flags. Further traversal occurs relative to currentNode even if it is not part of the current view, by applying the filters in the requested direction; if no traversal is possible, currentNode is not changed.
  - setCurrentNode
```
void setCurrentNode(Node currentNode)
             throws DOMException
```
    The node at which the TreeWalker is currently positioned.
    Alterations to the DOM tree may cause the current node to no longer be accepted by the TreeWalker's associated filter. currentNode may also be explicitly set to any node, whether or not it is within the subtree specified by the root node or would be accepted by the filter and whatToShow flags. Further traversal occurs relative to currentNode even if it is not part of the current view, by applying the filters in the requested direction; if no traversal is possible, currentNode is not changed.
    
    Throws:
    
    DOMException - NOT_SUPPORTED_ERR: Raised if an attempt is made to set currentNode to null.
  - parentNode
```
Node parentNode()
```
    Moves to and returns the closest visible ancestor node of the current node. If the search for parentNode attempts to step upward from the TreeWalker's root node, or if it fails to find a visible ancestor node, this method retains the current position and returns null.
    
    Returns:
    
    The new parent node, or null if the current node has no parent in the TreeWalker's logical view.
  - firstChild
```
Node firstChild()
```
    Moves the TreeWalker to the first visible child of the current node, and returns the new node. If the current node has no visible children, returns null, and retains the current node.
    
    Returns:
    
    The new node, or null if the current node has no visible children in the TreeWalker's logical view.
  - lastChild
```
Node lastChild()
```
    Moves the TreeWalker to the last visible child of the current node, and returns the new node. If the current node has no visible children, returns null, and retains the current node.
    
    Returns:
    
    The new node, or null if the current node has no children in the TreeWalker's logical view.
  - previousSibling
```
Node previousSibling()
```
    Moves the TreeWalker to the previous sibling of the current node, and returns the new node. If the current node has no visible previous sibling, returns null, and retains the current node.
    
    Returns:
    
    The new node, or null if the current node has no previous sibling. in the TreeWalker's logical view.
  - nextSibling
```
Node nextSibling()
```
    Moves the TreeWalker to the next sibling of the current node, and returns the new node. If the current node has no visible next sibling, returns null, and retains the current node.
    
    Returns:
    
    The new node, or null if the current node has no next sibling. in the TreeWalker's logical view.
  - previousNode
```
Node previousNode()
```
    Moves the TreeWalker 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 previousNode attempts to step upward from the TreeWalker's root node, returns null, and retains the current node.
    
    Returns:
    
    The new node, or null if the current node has no previous node in the TreeWalker's logical view.
  - nextNode
```
Node nextNode()
```
    Moves the TreeWalker 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 TreeWalker's root node, returns null, and retains the current node.
    
    Returns:
    
    The new node, or null if the current node has no next node in the TreeWalker's logical view.

Java Module java.xml Package org.w3c.dom.traversal Interface TreeWalker（JDK11）

Interface TreeWalker

Method Summary

Method Detail

getRoot

getWhatToShow

getFilter

getExpandEntityReferences

getCurrentNode

setCurrentNode

parentNode

firstChild

lastChild

previousSibling

nextSibling

previousNode

nextNode