Package org.apache.derby.impl.sql.compile

Class CollectNodesVisitor<T extends Visitable>

java.lang.Object

org.apache.derby.impl.sql.compile.CollectNodesVisitor<T>

All Implemented Interfaces:

Visitor

public class CollectNodesVisitor<T extends Visitable>
extends Object
implements Visitor

Collect all nodes of the designated type to be returned in a list.

Can find any type of node -- the class or class name of the target node is passed in as a constructor parameter.

Field Summary

Fields

Modifier and Type	Field	Description
private final Class<T>	nodeClass
private final List<T>	nodeList
private final Class<? extends Visitable>	skipOverClass

Constructor Summary

Constructors

Constructor	Description
CollectNodesVisitor(Class<T> nodeClass)	Construct a visitor
CollectNodesVisitor(Class<T> nodeClass, Class<? extends Visitable> skipOverClass)	Construct a visitor

Method Summary

Modifier and Type	Method	Description
List<T>	getList()	Return the list of matching nodes.
boolean	skipChildren(Visitable node)	Don't visit children under the skipOverClass node, if it isn't null.
boolean	stopTraversal()	Method that is called to see if query tree traversal should be stopped before visiting all nodes.
Visitable	visit(Visitable node)	If we have found the target node, we are done.
boolean	visitChildrenFirst(Visitable node)	Method that is called to see if visit() should be called on the children of node before it is called on node itself.

Methods inherited from class java.lang.Object

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

Field Details

nodeList

private final List<T extends Visitable> nodeList

nodeClass

private final Class<T extends Visitable> nodeClass

skipOverClass

private final Class<? extends Visitable> skipOverClass

Constructor Details

CollectNodesVisitor

public CollectNodesVisitor(Class<T> nodeClass)

Construct a visitor

Parameters:

nodeClass - the class of the node that we are looking for.

CollectNodesVisitor

public CollectNodesVisitor(Class<T> nodeClass,
 Class<? extends Visitable> skipOverClass)

Construct a visitor

Parameters:

nodeClass - the class of the node that we are looking for.

skipOverClass - do not go below this node when searching for nodeClass.

Method Details

visitChildrenFirst

public boolean visitChildrenFirst(Visitable node)

Description copied from interface: Visitor

Method that is called to see if visit() should be called on the children of node before it is called on node itself. If this method always returns true, the visitor will walk the tree bottom-up. If it always returns false, the tree is visited top-down.

Specified by:

visitChildrenFirst in interface Visitor

Parameters:

node - the top node of a sub-tree about to be visited

Returns:

true if node's children should be visited before node, false otherwise

stopTraversal

public boolean stopTraversal()

Description copied from interface: Visitor

Method that is called to see if query tree traversal should be stopped before visiting all nodes. Useful for short circuiting traversal if we already know we are done.

Specified by:

stopTraversal in interface Visitor

Returns:

true/false

visit

public Visitable visit(Visitable node)

If we have found the target node, we are done.

Specified by:

visit in interface Visitor

Parameters:

node - the node to process

Returns:

me

skipChildren

public boolean skipChildren(Visitable node)

Don't visit children under the skipOverClass node, if it isn't null.

Specified by:

skipChildren in interface Visitor

Parameters:

node - the node to process

Returns:

true/false

getList

public List<T> getList()

Return the list of matching nodes. The returned list may be empty, if there are no matching nodes. It is never null.