上一章链接：

《HeadFirst设计模式(第二版)》第九章代码——迭代器模式_轩下小酌的博客-CSDN博客

        前面说到，当一个菜单里面出现了子菜单的时候，前面的迭代器模式得换成组合模式。

组合模式：

        允许将对象组合成树形结构来表现部分-整体层次结构。组合让用户可以统一处理个别对象和对象组合。

代码文件结构：

 

MenuComponent

package Chapter9_CompositePattern;

/**
 * @Author 竹心
 * @Date 2023/8/18
 **/

public abstract class MenuComponent {
    public void add(MenuComponent menuComponent) {
        throw new UnsupportedOperationException();
    }
    public void remove(MenuComponent menuComponent) {
        throw new UnsupportedOperationException();
    }
    public MenuComponent getChild(int i) {
        throw new UnsupportedOperationException();
    }

    public String getName() {
        throw new UnsupportedOperationException();
    }
    public String getDescription() {
        throw new UnsupportedOperationException();
    }
    public double getPrice() {
        throw new UnsupportedOperationException();
    }
    public boolean isVegetarian() {
        throw new UnsupportedOperationException();
    }

    public void print() {
        throw new UnsupportedOperationException();
    }
}

MenuItem

package Chapter9_CompositePattern;

/**
 * @Author 竹心
 * @Date 2023/8/18
 **/

public class MenuItem extends MenuComponent{
    String name;
    String description;
    boolean vegetarian;
    double price;

    public MenuItem(String name,
                    String description,
                    boolean vegetarian,
                    double price)
    {
        this.name = name;
        this.description = description;
        this.vegetarian = vegetarian;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public String getDescription() {
        return description;
    }

    public double getPrice() {
        return price;
    }

    public boolean isVegetarian() {
        return vegetarian;
    }

    public void print() {
        System.out.print("  " + getName());
        if (isVegetarian()) {
            System.out.print("(v)");
        }
        System.out.println(", " + getPrice());
        System.out.println("     -- " + getDescription());
    }
}

Menu

package Chapter9_CompositePattern;

import java.util.ArrayList;
import java.util.Iterator;

/**
 * @Author 竹心
 * @Date 2023/8/18
 **/

public class Menu extends MenuComponent{
    //菜单组合
    ArrayList<MenuComponent> menuComponents = new ArrayList<MenuComponent>();
    String name;
    String description;

    public Menu(String name, String description) {
        this.name = name;
        this.description = description;
    }

    public void add(MenuComponent menuComponent) {
        menuComponents.add(menuComponent);
    }

    public void remove(MenuComponent menuComponent) {
        menuComponents.remove(menuComponent);
    }

    public MenuComponent getChild(int i) {
        return (MenuComponent)menuComponents.get(i);
    }

    public String getName() {
        return name;
    }

    public String getDescription() {
        return description;
    }

    public void print() {
        System.out.print("\n" + getName());
        System.out.println(", " + getDescription());
        System.out.println("---------------------");

        //这里递归打印
        Iterator<MenuComponent> iterator = menuComponents.iterator();
        while (iterator.hasNext()) {
            MenuComponent menuComponent =
                    (MenuComponent)iterator.next();
            menuComponent.print();
        }
    }
}

Waitress 

package Chapter9_CompositePattern;

/**
 * @Author 竹心
 * @Date 2023/8/18
 **/

public class Waitress {
    MenuComponent allMenus;//菜单根节点

    public Waitress(MenuComponent allMenus) {
        this.allMenus = allMenus;
    }

    public void printMenu() {
        allMenus.print();
    }
}

MenuTestDrive

package Chapter9_CompositePattern;

/**
 * @Author 竹心
 * @Date 2023/8/18
 **/

public class MenuTestDrive {
    public static void main(String args[]) {
        MenuComponent pancakeHouseMenu =
                new Menu("PANCAKE HOUSE MENU", "Breakfast");
        MenuComponent dinerMenu =
                new Menu("DINER MENU", "Lunch");
        MenuComponent cafeMenu =
                new Menu("CAFE MENU", "Dinner");
        MenuComponent dessertMenu =
                new Menu("DESSERT MENU", "Dessert of course!");
        MenuComponent coffeeMenu = new Menu("COFFEE MENU", "Stuff to go with your afternoon coffee");

        MenuComponent allMenus = new Menu("ALL MENUS", "All menus combined");

        allMenus.add(pancakeHouseMenu);
        allMenus.add(dinerMenu);
        allMenus.add(cafeMenu);

        pancakeHouseMenu.add(new MenuItem(
                "K&B's Pancake Breakfast",
                "Pancakes with scrambled eggs and toast",
                true,
                2.99));

        dinerMenu.add(new MenuItem(
                "Vegetarian BLT",
                "(Fakin') Bacon with lettuce & tomato on whole wheat",
                true,
                2.99));

        dinerMenu.add(dessertMenu);

        dessertMenu.add(new MenuItem(
                "Apple Pie",
                "Apple pie with a flakey crust, topped with vanilla icecream",
                true,
                1.59));

        cafeMenu.add(coffeeMenu);

        coffeeMenu.add(new MenuItem(
                "Coffee Cake",
                "Crumbly cake topped with cinnamon and walnuts",
                true,
                1.59));

        Waitress waitress = new Waitress(allMenus);//这示例代码怎么这么多。。。

        waitress.printMenu();
    }
}