Visitor Design Pattern

Visitor Pattern is a type of behavioral design pattern. Wikipedia says: the visitor design pattern is a way of separating analgorithm from an object structure it operates on. A practical result of this separation is the ability to add new operations to existing object structures without modifying those structures.

Example:



Class A{

public void accept(Visitor v){

v.visit();

}

...

}

public interface Visitor {

public void visit(Class1 c);

public void visit(Class2 c);

...

}

public class CallingClass implements Visitor{

A objA;

SomeMethod(){

//as soon as following line is called, the visit class is called from objA

objA.accept(this);

....

}

public void visit(Class1 c){

...

}

public void visit(Class2 c){

...

}

}