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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();}
}