算法和数据结构分开__访问者模式___Visitor
package com.ding.shejimoshi.Visitor;

abstract class Visitor {

public abstract void visitConcreteElementA(ConcreteElementA concreteElementA);
public abstract void visitConcreteElementB(ConcreteElementB concreteElementB);


}
package com.ding.shejimoshi.Visitor;

public class ConcreteVisitor1 extends Visitor{

public void visitConcreteElementA(ConcreteElementA concreteElementA){

System.out.println(concreteElementA.getClass()+"被"+this.getClass()+"访问");
}
public void visitConcreteElementB(ConcreteElementB concreteElementB){

System.out.println(concreteElementB.getClass()+"被"+this.getClass()+"访问");
}
}
package com.ding.shejimoshi.Visitor;

public class ConcreteVisitor2 extends Visitor{
public void visitConcreteElementA(ConcreteElementA concreteElementA){

System.out.println(concreteElementA.getClass()+"被"+this.getClass()+"访问");
}
public void visitConcreteElementB(ConcreteElementB concreteElementB){

System.out.println(concreteElementB.getClass()+"被"+this.getClass()+"访问");
}
}
package com.ding.shejimoshi.Visitor;

abstract class Element {
public abstract void accept(Visitor visitor);
}
package com.ding.shejimoshi.Visitor;

public class ConcreteElementA extends Element{

public void accept(Visitor visitor){
visitor.visitConcreteElementA(this);
}
}
package com.ding.shejimoshi.Visitor;

public class ConcreteElementB extends Element{

public void accept(Visitor visitor){
visitor.visitConcreteElementB(this);
}
}
package com.ding.shejimoshi.Visitor;

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

public class ObjectStructure {
private List<Element> elements=new ArrayList<Element>();

public void attace(Element element){
elements.add(element);
}
public void detach(Element element){
elements.remove(element);
}

public void accept(Visitor visitor){
for(Element s :elements){
s.accept(visitor);
}

}

}
package com.ding.shejimoshi.Visitor;

public class Main {


public static void main(String [] args){

ObjectStructure o=new ObjectStructure();

o.attace(new ConcreteElementA());
o.attace(new ConcreteElementB());
ConcreteVisitor1 v1=new ConcreteVisitor1();
ConcreteVisitor2 v2=new ConcreteVisitor2();
o.accept(v1);
o.accept(v2);
}
}

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class com.ding.shejimoshi.Visitor.ConcreteElementA被class com.ding.shejimoshi.Visitor.ConcreteVisitor1访问
class com.ding.shejimoshi.Visitor.ConcreteElementB被class com.ding.shejimoshi.Visitor.ConcreteVisitor1访问
class com.ding.shejimoshi.Visitor.ConcreteElementA被class com.ding.shejimoshi.Visitor.ConcreteVisitor2访问
class com.ding.shejimoshi.Visitor.ConcreteElementB被class com.ding.shejimoshi.Visitor.ConcreteVisitor2访问
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访问者模式 优点 数据结构和算法分开

缺点 不要增加新的数据结构

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private List<Element> elements=new ArrayList<Element>();

类的集合