org.coinjema.collections
Interface HashTreeTraverser<T>

All Known Implementing Classes:

SearchByClass, TreeSorter

public interface HashTreeTraverser<T>

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.

Version:

$Revision: 1.1 $

Author:

Michael Stover (mstover1 at apache.org)

See Also:

HashTree, SearchByClass

Method Summary

void	addNode(T node, HashTree<T> 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(T node,
             HashTree<T> 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.