Java Doc for HierarchicalASTVisitor.java in  » IDE-Eclipse » jdt » org » eclipse » jdt » internal » corext » dom » Java Source Code / Java DocumentationJava Source Code and Java Documentation

This class has a visit(XX node) method for every for every class (concrete or abstract) XX in the ASTNode hierarchy. In this class' default implementations of these methods, the method corresponding to a given ASTNode descendant class will call (and return the return value of) the visit(YY) method for it's superclass YY, with the exception of the visit(ASTNode) method which simply returns true, since ASTNode doesn't have a superclass that is within the ASTNode hierarchy.

Because of this organization, when visit(XX) methods are overridden in a subclass, and the visitor is applied to a node, only the most specialized overridden method implementation for the node's type will be called, unless this most specialized method calls other visit methods (this is discouraged) or, (preferably) calls super.visit(XX node), (the reference type of the parameter must be XX) which will invoke this class' implementation of the method, which will, in turn, invoke the visit(YY) method corresponding to the superclass, YY.

Thus, the dispatching behaviour achieved when HierarchicalASTVisitors' visit(XX) methods, corresponding to a particular concrete or abstract ASTNode descendant class, are overridden is exactly analogous to the dispatching behaviour obtained when method implementations are added to the same ASTNode descendant classes.