org.perfectjpattern.core.api.behavioral.visitor
Interface IElement

public interface IElement

Visitor Design Pattern: Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.

Responsibility Abstract definition of "Element"

• Marker interface for any Element type.

Example usage:

    //
    // Abstract Base Node for a simple Element hierarchy.
    //  
    abstract
    class AbstractNode 
    implements IElement 
    {
        //--------------------------------------------------------------------
        public 
        BaseNode(String aName) 
        {
            theName = aName;
        }
                
        //--------------------------------------------------------------------
        public final String 
        getName() 
        {
            return theName;
        }        

        //--------------------------------------------------------------------
        // members
        //--------------------------------------------------------------------
        private final String theName;
    }

    //
    // RedNode
    //  
    class RedNode 
    extends AbstractNode 
    {
        //--------------------------------------------------------------------
        public 
        RedNode() 
        {
            super("Red");
        }
    }
    
    //
    // BlackNode
    //  
    class BlackNode 
    extends AbstractNode 
    {
        //--------------------------------------------------------------------
        public 
        BlackNode() 
        {
            super("Black");
        }
    }
    
    //
    // Simple Visitor
    // 
    class NodeVisitor
    extends AbstractVisitor<AbstractNode>
    {
        //--------------------------------------------------------------------
        public void
        visitRedNode(RedNode aNode)
        {
             // do RedNode visiting
             System.out.println(aNode.getName());    
        }
        
        //--------------------------------------------------------------------
        public void
        visitBlackNode(BlackNode aNode)
        {
             // do BlackNode visiting
             System.out.println(aNode.getName());    
        }
    }
    
    //
    // Usage example
    //
    IVisitor<AbstractNode> myVisitor = new NodeVisitor();
    myVisitor.visit(new RedNode());
    myVisitor.visit(new BlackNode());
 

Version:

$Revision: 1.0 $ $Date: Jul 1, 2007 6:59:35 AM $

Author:

Giovanni Azua