org.apache.jorphan.collections

## Interface HashTreeTraverser

- All Known Implementing Classes:
    CheckDirty, ComponentTreeClonerForValidation, ConvertListeners, FindTestElementsUpToRootTraverser, PreCompiler, SearchByClass, TestCompiler, TreeCloner, TreeClonerForValidation, TreeClonerNoTimer, TurnElementsOn

      public interface HashTreeTraverser

  By implementing this interface, a class can easily traverse a HashTree object, and be notified via callbacks of certain events. There are three such events:
  1. When a node is first encountered, the traverser's `addNode(Object,HashTree)` method is called. It is handed the object at that node, and the entire sub-tree of the node.
  2. When a leaf node is encountered, the traverser is notified that a full path has been finished via the `processPath()` method. It is the traversing class's responsibility to know the path that has just finished (this can be done by keeping a simple stack of all added nodes).
  3. When a node is retraced, the traverser's `subtractNode()` is called. Again, it is the traverser's responsibility to know which node has been retraced.
  To summarize, as the traversal goes down a tree path, nodes are added. When the end of the path is reached, the `processPath()` call is sent. As the traversal backs up, nodes are subtracted.

  The traversal is a depth-first traversal.

  See Also:
    `HashTree`, `SearchByClass`

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addNode(Object node, HashTree subTree)` The tree traverses itself depth-first, calling addNode for each object it encounters as it goes.
    `void` | `processPath()` Process path is called when a leaf is reached.
    `void` | `subtractNode()` Indicates traversal has moved up a step, and the visitor should remove the top node from its stack structure.

- - ### Method Detail

    - #### addNode

          void addNode(Object node,
                       HashTree subTree)

      The tree traverses itself depth-first, calling addNode for each object it encounters as it goes. This is a callback method, and should not be called except by a HashTree during traversal.
      Parameters:
        `node` - the node currently encountered
        `subTree` - the HashTree under the node encountered

    - #### subtractNode

          void subtractNode()

      Indicates traversal has moved up a step, and the visitor should remove the top node from its stack structure. This is a callback method, and should not be called except by a HashTree during traversal.

    - #### processPath

          void processPath()

      Process path is called when a leaf is reached. If a visitor wishes to generate Lists of path elements to each leaf, it should keep a Stack data structure of nodes passed to it with addNode, and removing top items for every `subtractNode()` call. This is a callback method, and should not be called except by a HashTree during traversal.

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