Package org.apache.commons.configuration2.tree

Class NodeTreeWalker

java.lang.Object

org.apache.commons.configuration2.tree.NodeTreeWalker

public class NodeTreeWalker
extends Object

A class providing different algorithms for traversing a hierarchy of configuration nodes.

The methods provided by this class accept a ConfigurationNodeVisitor and visit all nodes in a hierarchy starting from a given root node. Because a NodeHandler has to be passed in, too, arbitrary types of nodes can be processed. The walk() methods differ in the order in which nodes are visited. Details can be found in the method documentation.

An instance of this class does not define any state; therefore, it can be shared and used concurrently. The INSTANCE member field can be used for accessing a default instance. If desired (e.g. for testing purposes), new instances can be created.

Since:

2.0

Field Summary

Fields

Modifier and Type	Field	Description
static final NodeTreeWalker	INSTANCE	The default instance of this class.

Constructor Summary

Constructors

Constructor	Description
NodeTreeWalker()

Method Summary

Modifier and Type	Method	Description
<T> void	walkBFS(T root, ConfigurationNodeVisitor<T> visitor, NodeHandler<T> handler)	Visits all nodes in the hierarchy represented by the given root node in breadth first search manner.
<T> void	walkDFS(T root, ConfigurationNodeVisitor<T> visitor, NodeHandler<T> handler)	Visits all nodes in the hierarchy represented by the given root node in depth first search manner.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

INSTANCE

public static final NodeTreeWalker INSTANCE

The default instance of this class.

Constructor Details

NodeTreeWalker

public NodeTreeWalker()

Method Details

walkBFS

public <T> void walkBFS(T root,
 ConfigurationNodeVisitor<T> visitor,
 NodeHandler<T> handler)

Visits all nodes in the hierarchy represented by the given root node in breadth first search manner. This means that the nodes are visited in an order corresponding to the distance from the root node: first the root node is visited, then all direct children of the root node, then all direct children of the first child of the root node, etc. In this mode of traversal, there is no direct connection between the encounter of a node and its children. Therefore, on the visitor object only the visitBeforeChildren() method gets called!.

Type Parameters:

T - the type of the nodes involved

Parameters:

root - the root node of the hierarchy to be processed (may be null, then this call has no effect)

visitor - the ConfigurationNodeVisitor (must not be null)

handler - the NodeHandler (must not be null)

Throws:

IllegalArgumentException - if a required parameter is null

walkDFS

public <T> void walkDFS(T root,
 ConfigurationNodeVisitor<T> visitor,
 NodeHandler<T> handler)

Visits all nodes in the hierarchy represented by the given root node in depth first search manner. This means that first ConfigurationNodeVisitor.visitBeforeChildren(Object, NodeHandler) is called on a node, then recursively all of its children are processed, and eventually ConfigurationNodeVisitor.visitAfterChildren(Object, NodeHandler) gets invoked.

Type Parameters:

T - the type of the nodes involved

Parameters:

root - the root node of the hierarchy to be processed (may be null, then this call has no effect)

visitor - the ConfigurationNodeVisitor (must not be null)

handler - the NodeHandler (must not be null)

Throws:

IllegalArgumentException - if a required parameter is null