de.hunsicker.jalopy.language
Class TreeWalker

java.lang.Object
  |
  +--de.hunsicker.jalopy.language.TreeWalker

Direct Known Subclasses:

CodeInspector

public abstract class TreeWalker

extends Object

Helper class to make implementing tree walkers easy.

To implement a class that walks over all nodes simply dereive from TreeWalker and implement the callback method visit(de.hunsicker.antlr.collections.AST).

 class MyWalker
     extends TreeWalker
 {
     // called for every node
     public void visit(AST node)
     {
         System.out.println("node visited: " + node);
     }
 }
 

If you want to control which nodes will be actually visited, overwrite walkNode(de.hunsicker.antlr.collections.AST) too.

 // visits only IMPORT nodes and quits after the last IMPORT node found
 protected void walkNode(AST node)
 {
     switch (node.getType())
     {
         case JavaTokenTypes.ROOT:
             // skip to next child
             walkNode(node.getFirstChild());
             break;
 
         case JavaTokenTypes.PACKAGE_DEF:
             // skip to next child
             walkNode(node.getNextSibling());
             break;
 
        case JavaTokenTypes.IMPORT:
             // only visit root node, DON'T walk over it's children
             visit(node);
 
             // continue with the next node
             walkNode(node.getNextSibling());
             break;
 
         case JavaTokenTypes.CLASS_DEF:
             // quit after the first non-IMPORT node
             return;
     }
 }
 

Version:

$Revision: 1.2 $

Author:

Marco Hunsicker

Field Summary

protected boolean

stop Indicates a stop.

Constructor Summary

protected

TreeWalker() Creates a new TreeWalker object.

Method Summary

void	reset() Resets the walker.
protected void	stop() Stops the walking.
abstract void	visit(AST node) Callback method that can be called for a node found.
void	walk(AST tree) Starts the walking with the root node of the tree or node portion.
protected void	walkChildren(AST node) Iterates over all children of the given node.
protected void	walkNode(AST node) Walks over the given node.

Methods inherited from class java.lang.Object

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

Field Detail

stop

protected boolean stop

Indicates a stop.

Constructor Detail

TreeWalker

protected TreeWalker()

Creates a new TreeWalker object.

Method Detail

reset

public void reset()

Resets the walker.

visit

public abstract void visit(AST node)

Callback method that can be called for a node found. Overwrite to perform whatever action you want take place for a node.

In the default implementation, this method will be called for every node of the tree.

Parameters:

node - a node of the tree.

walk

public void walk(AST tree)

Starts the walking with the root node of the tree or node portion.

Parameters:

tree - the tree to walk over.

stop

protected void stop()

Stops the walking. You have to reset the walker prior reusing it.

See Also:

reset()

walkChildren

protected void walkChildren(AST node)

Iterates over all children of the given node.

Parameters:

node - node to iterate over.

walkNode

protected void walkNode(AST node)

Walks over the given node. Links in children. Called for every single node of the tree. The default implemention simply calls

 visit(node);
 walkChildren();
 

to visit the current node and continue walking over all children of the node.

Parameters:

node - a node of the tree.