Visitor 访问者模式

package wang.jinggo.basics.zhss.visitor;

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

/**
 * @author: wangyj
 * @create: 2021-10-25
 * @version: 1.0.0
 **/
public class VisitorPatternDemo {

    public static void main(String[] args) {
        Department leafDept1 = new Department("叶子部门1");
        Department leafDept2 = new Department("叶子部门2");
        Department leafDept3 = new Department("叶子部门3");

        Department subDept1 = new Department("子部门1");
        subDept1.getChildren().add(leafDept1);
        subDept1.getChildren().add(leafDept2);

        Department subDept2 = new Department("子部门2");
        subDept2.getChildren().add(leafDept3);

        Department parentDept = new Department("父部门");
        parentDept.getChildren().add(subDept1);
        parentDept.getChildren().add(subDept2);

        Visitor removeVisitor = new RemoveVisitor();
        parentDept.accept(removeVisitor);

        Visitor updateStatusVisitor = new UpdateStatusVisitor("禁用");
        parentDept.accept(updateStatusVisitor);

        // 访问者模式，一般来说，就是跟组合模式结合起来使用的
        // 组合模式代表了一种复杂的对象的类型
        // 如果你后面要给树形的数据结构增加个什么功能，修改代码可能会比较麻烦
        // 但是如果采用访问者模式来做，你可以在任何时候给树形的数据结构增加任何的功能
    }

    public static class Department {

        private String name;
        private List<Department> children = new ArrayList<Department>();

        public Department(String name) {
            super();
            this.name = name;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public List<Department> getChildren() {
            return children;
        }

        public void setChildren(List<Department> children) {
            this.children = children;
        }

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

    }

    public interface Visitor {

        void visit(Department dept);

    }

    public static class RemoveVisitor implements Visitor {

        public void visit(Department dept) {
            if (dept.getChildren().size() > 0) {
                for (Department child : dept.getChildren()) {
                    child.accept(this);
                }
            }
            System.out.println("删除部门【" + dept.getName() + "】");
        }

    }

    public static class UpdateStatusVisitor implements Visitor {

        private String status;

        public void visit(Department dept) {
            if (dept.getChildren().size() > 0) {
                for (Department child : dept.getChildren()) {
                    child.accept(this);
                }
            }
            System.out.println("将部门【" + dept.getName() + "】的状态修改为：" + status);
        }

        public UpdateStatusVisitor(String status) {
            this.status = status;
        }

    }

}