设计模式之---访问者模式

package visitor;

public abstract class Element {
public abstract void accept(IVisitor visitor);
public abstract void doSomething();
}

package visitor;

public class Visitor implements IVisitor {

@Override
public void visit(Element element) {
// TODO Auto-generated method stub
System.out.println("对element中的数据进行操作");
element.doSomething();
}

}

package visitor;

public class ConcreteElement0 extends Element {

@Override
public void accept(IVisitor visitor) {
// TODO Auto-generated method stub
visitor.visit(this); //这是关键 利用双分派技术实现处理与数据结构的分离
}

@Override
public void doSomething() {
// TODO Auto-generated method stub
System.out.println("这是元素0的方法");
}

}

package visitor;

public class ConcreteElement1 extends Element {

@Override
public void accept(IVisitor visitor) {
// TODO Auto-generated method stub
visitor.visit(this); //这是关键 利用双分派技术实现处理与数据结构的分离
}

@Override
public void doSomething() {
// TODO Auto-generated method stub
System.out.println("这是元素1的方法");
}

}

package visitor;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class ObjectStruture {
public static List<Element> getList(){
List<Element> list = new ArrayList<Element>();
Random ran = new Random();
for(int i=0; i<10; i++){
int a = ran.nextInt(100);
if(a>50){
list.add(new ConcreteElement0());
}else{
list.add(new ConcreteElement1());
}
}
return list;
}
}

package visitor;

import java.util.List;

public class Client {

public static void main(String[] args) {
// TODO Auto-generated method stub
List<Element> list = ObjectStruture.getList();
for(Element e: list){
e.accept(new Visitor());
}
}

}