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设计模式-访问者模式

java 2025/7/1 9:31:20

一.所用到的类

访问者模式是一个多对多的关系

1.所要被访问的类

一个公共抽象类：属性和accept方法，用来接收访问者
实现抽象类的N个类

2.访问者类

一个抽象接口里面定义要访问N个类的方法
实现抽象接口的 N个类

二、是实现代码

所要被访问的类的抽象类

public abstract class User {public String name;public String identity; // 身份public String clazz;public User(String name, String identity, String clazz){this.name = name;this.identity = identity;this.clazz = clazz;}public abstract void accept(Visitor visitor);
}

所要被访问的类1

public class Student extends User{public Student(String name, String identity, String clazz){super(name, identity, clazz);}@Overridepublic void accept(Visitor visitor) {visitor.visit(this);}
}

所要被访问的类2

public class Teacher extends User{public Teacher(String name, String identity, String clazz) {super(name, identity, clazz);}@Overridepublic void accept(Visitor visitor) {visitor.visit(this);}
}

访问类的接口

public interface Visitor {public void visit(Student student);public void visit(Teacher teacher);
}

访问类的实现类1

public class Parent implements Visitor{@Overridepublic void visit(Student student) {System.out.println("学生" + student.name + "，老师" + student.clazz );}@Overridepublic void visit(Teacher teacher) {System.out.println("老师" + teacher.name + "，身份" + teacher.clazz );}
}

访问类的实现类2

public class Principal implements Visitor{@Overridepublic void visit(Student student) {System.out.println("学生" + student.name + "的学号是：" + student.identity);}@Overridepublic void visit(Teacher teacher) {System.out.println("老师" + teacher.name + "班级：" + teacher.clazz);}
}

调用类

@SpringBootApplication
public class VisitorApplication {public static void main(String[] args) {User student = new Student("小王", "20250101", "一年一班");User teacher = new Teacher("李老师", "高级老师", "仨年一班");Visitor principal = new Principal();System.out.println("校长开始");student.accept(principal);teacher.accept(principal);System.out.println("\n家长开始");Visitor parent = new Parent();student.accept(parent);teacher.accept(parent);}
}