算法和数据结构分开__访问者模式___Visitor
AHRL 2011-02-17
packagecom.ding.shejimoshi.Visitor;
abstractclassVisitor{
publicabstractvoidvisitConcreteElementA(ConcreteElementAconcreteElementA);
publicabstractvoidvisitConcreteElementB(ConcreteElementBconcreteElementB);
}
packagecom.ding.shejimoshi.Visitor;
publicclassConcreteVisitor1extendsVisitor{
publicvoidvisitConcreteElementA(ConcreteElementAconcreteElementA){
System.out.println(concreteElementA.getClass()+"被"+this.getClass()+"访问");
}
publicvoidvisitConcreteElementB(ConcreteElementBconcreteElementB){
System.out.println(concreteElementB.getClass()+"被"+this.getClass()+"访问");
}
}
packagecom.ding.shejimoshi.Visitor;
publicclassConcreteVisitor2extendsVisitor{
publicvoidvisitConcreteElementA(ConcreteElementAconcreteElementA){
System.out.println(concreteElementA.getClass()+"被"+this.getClass()+"访问");
}
publicvoidvisitConcreteElementB(ConcreteElementBconcreteElementB){
System.out.println(concreteElementB.getClass()+"被"+this.getClass()+"访问");
}
}
packagecom.ding.shejimoshi.Visitor;
abstractclassElement{
publicabstractvoidaccept(Visitorvisitor);
}
packagecom.ding.shejimoshi.Visitor;
publicclassConcreteElementAextendsElement{
publicvoidaccept(Visitorvisitor){
visitor.visitConcreteElementA(this);
}
}
packagecom.ding.shejimoshi.Visitor;
publicclassConcreteElementBextendsElement{
publicvoidaccept(Visitorvisitor){
visitor.visitConcreteElementB(this);
}
}
packagecom.ding.shejimoshi.Visitor;
importjava.util.ArrayList;
importjava.util.List;
publicclassObjectStructure{
privateList<Element>elements=newArrayList<Element>();
publicvoidattace(Elementelement){
elements.add(element);
}
publicvoiddetach(Elementelement){
elements.remove(element);
}
publicvoidaccept(Visitorvisitor){
for(Elements:elements){
s.accept(visitor);
}
}
}
packagecom.ding.shejimoshi.Visitor;
publicclassMain{
publicstaticvoidmain(String[]args){
ObjectStructureo=newObjectStructure();
o.attace(newConcreteElementA());
o.attace(newConcreteElementB());
ConcreteVisitor1v1=newConcreteVisitor1();
ConcreteVisitor2v2=newConcreteVisitor2();
o.accept(v1);
o.accept(v2);
}
}
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classcom.ding.shejimoshi.Visitor.ConcreteElementA被classcom.ding.shejimoshi.Visitor.ConcreteVisitor1访问
classcom.ding.shejimoshi.Visitor.ConcreteElementB被classcom.ding.shejimoshi.Visitor.ConcreteVisitor1访问
classcom.ding.shejimoshi.Visitor.ConcreteElementA被classcom.ding.shejimoshi.Visitor.ConcreteVisitor2访问
classcom.ding.shejimoshi.Visitor.ConcreteElementB被classcom.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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privateList<Element>elements=newArrayList<Element>();
类的集合
