菜鸟硕枫设计模式系列之24 访问者模式

visit pattern是一种行为模式。主要特点是一个可遍历数据结构和比较稳固的对象，对于对象行为则可以方便添加，并且可以根据对象的类型表现不同的行为。

访问者模式类图：
[img]http://dl.iteye.com/upload/attachment/364939/55cf35cc-e52a-31ac-a1d1-d02bf7aec7fc.jpg[/img]


具体实现demo:
对象接口

package visitorPattern;

public interface Person {
	void accept(Visitor visitor);
}

具体对象

package visitorPattern;

public class Man implements Person{

	public void accept(Visitor visitor) {
		visitor.visit(this);
	}

}

具体对象2

package visitorPattern;

public class Woman implements Person{

	@Override
	public void accept(Visitor visitor) {

		visitor.visit(this);
	}

}

访问者接口：

package visitorPattern;

public interface Visitor {
	void visit(Man man);
	void visit(Woman woman);
}

package visitorPattern;

public class Shop implements Visitor{

	@Override
	public void visit(Man man) {
		System.out.println("Shopping is boring for " +man.getClass());
	}

	@Override
	public void visit(Woman woman) {
		// TODO Auto-generated method stub
		System.out.println("Shopping is funny for " +woman.getClass());
	}

}

package visitorPattern;

public class Work implements Visitor{

	@Override
	public void visit(Man man) {
		// TODO Auto-generated method stub
		System.out.println("Working is not so bad for " +man.getClass());
	}

	@Override
	public void visit(Woman woman) {
		// TODO Auto-generated method stub
		System.out.println("Working is quite a hard time for " +woman.getClass());
	}

}

测试类

package visitorPattern;

import java.util.ArrayList;

public class visitPatternTest {

	public static void main(String[]args){
		Man man = new Man();
		Woman woman = new Woman();
		ArrayList<Person> arrayList = new ArrayList<Person>();
		ObjectStructrue o1 = new ObjectStructrue(arrayList);
		o1.add(woman);
		o1.add(man);

		Work work = new Work();
		o1.show(work);
		System.out.println("------------------------------");
		Shop shop = new Shop();
		o1.show(shop);
	}
}

备注：优点在于很方便的添加访问者，而不用去改变对象的其他属性或是实现。