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设计模式学习--迭代器模式(Iterator Pattern)和组合模式（Composite Pattern)
阅读量：5105 次
发布时间：2019-06-13

本文共 25714 字，大约阅读时间需要 85 分钟。

设计模式学习--迭代器模式(Iterator Pattern)

概述

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迭代器模式提供一种方法顺序访问一个聚合对象中的各个元素，而又不暴露其内部的表示

把游走的任务放在迭代器上，而不是聚合上。这样简化了聚合的接口和实现，也让责任各得其所。

组合模式允许你将对象组成树形结构来表现“整体/部分”的层次结构。组合能让客户以一致的方式处理个别对象和对象组合。

OO原则

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  • 封装变化
  • 多用组合，少用继承
  • 针对接口编程，不针对实现编程
  • 为交互对象之间的松耦合设计而努力
  • 类应该对扩展开放，对修改关闭
  • 依赖抽象，不要依赖具体类
  • 只和朋友交谈
  • 别找我，我会找你
  • 类应该只有一个改变的理由

 

要点

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  • 迭代器允许访问聚合的元素，而不需要暴露它的内部结构
  • 迭代器将遍历聚合的工作封装进一个对象中。
  • 当使用迭代器的时候，我们依赖聚合提供遍历。
  • 迭代器提供一个通用的接口，让我们遍历聚合的项，当我们编码使用聚合的项时，就可以使用多态机制。
  • 我们应该努力让一个类分配一个责任。
  • 组合模式提供一个结构，可同时包容个别对象和组合对象。
  • 组合模式允许客户对个别对象以及组合对象一视同仁。
  • 组合结构内的任意对象成为组件，组件可以是组合，也可以是叶节点。
  • 在实现组合模式时，有许多设计上的折衷。你要根据需要平衡透明性和安全性。

 

例子1

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自定义迭代器

Iterator

 

package dinermerger;/** * 自定义迭代器接口 * @author wwj * */public interface Iterator {	boolean hasNext();		//是否还有下一个元素	Object next();			//返回下一个元素}

实现迭代器

 

DinerMenuIterator

 

package dinermerger;/** * 实现一个具体的迭代器，为餐厅菜单服务 * @author Administrator * */public class DinerMenuIterator implements Iterator {	MenuItem[] items;	int position = 0;	//记录当前数组遍历的位置		public DinerMenuIterator(MenuItem[] items) {		this.items = items;	}	@Override	public boolean hasNext() {		if(position >= items.length || items[position] == null) {			return false;		} else {			return true;		}	}	@Override	public Object next() {		MenuItem menuItem = items[position];		position = position + 1;		return menuItem;	}}

 

PancakeHouseMenuIterator 

package dinermerger;import java.util.ArrayList;/** * 煎饼屋菜单实现 * @author wwj * */public class PancakeHouseMenuIterator implements Iterator{	ArrayList menuItems;	int position = 0;		public PancakeHouseMenuIterator(ArrayList menuItems) {		this.menuItems = menuItems;	}	@Override	public boolean hasNext() {		if(position >= menuItems.size()) {			return false;		} else {			return true;		}	}	@Override	public Object next() {		Object object = menuItems.get(position);		position = position + 1;		return object;	}}

菜单项

 

package dinermerger;/** * 菜单项 * @author wwj * */public class MenuItem {	String name;		//名称	String description;	//叙述	boolean vegetarian;	//是否为素食	double price;		//价格		/*	 * 将这些值传入构造器来初始化这个菜单项	 */	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;	}			}

菜单

 

PancakeHouseMenu

 

package dinermerger;import java.util.ArrayList;/** * 煎饼屋菜单实现 * @author wwj * */public class PancakeHouseMenu {	ArrayList menuItems;	public PancakeHouseMenu() {		menuItems = new ArrayList();				addItem("K&B's Pancake Breakfast", "Pancakes with scrambled eggs, and toast", true, 2.99);				addItem("Regular Pancake Breakfast", "Pancakes with fried eggs, sausage", false, 2.99);				addItem("Blueberry Pancakes", "Pancakes made with fresh blueberries", true, 3.49);				addItem("Waffles", "Waffles, with your choice of blueberries or strawberries", true, 3.59);			}		/**	 * 创建一个新的菜单项对象，传入每一个变量，然后将它加入到ArrayList中	 * @param name	菜名	 * @param description 叙述	 * @param vegetarian  是否为素食	 * @param price	价格	 */	public void addItem(String name, String description, boolean vegetarian, double price) {		MenuItem menuItem = new MenuItem(name, description, vegetarian, price);		menuItems.add(menuItem);	}	/*	public ArrayList getMenuItems() {		return menuItems;	}*/			public Iterator createIterator() {		return new PancakeHouseMenuIterator(menuItems);	}}

 

DinerMenu 

package dinermerger;/** * 餐厅菜单 * @author wwj * */public class DinerMenu {	static final int MAX_ITEMS = 6;	int numberOfItems = 0;	MenuItem[] menuItems;		//使用一个数组，所以可以控制菜单的长度，并且在取出菜单项的时候，不需要转型			public DinerMenu() {		menuItems = new MenuItem[MAX_ITEMS];		addItem("Vegetarian BLT",				"(Fakin') Bacon with lettuce & tomato on Whole wheat", true,				2.99);		addItem("BLT", "Bacon with lettuce & tomato on Whole wheat", false,				2.99);		addItem("Soup of the day",				"Soup of the day, with a side of potato salad", false, 3.29);		addItem("Hotdog",				"A hot dog, with saurkraut, relish, onions, topped with cheese",				false, 3.05);		addItem("Steamed Veggies and Brown Rice",				"Steamed vegetables over brown rice", true, 3.99);		addItem("Pasta",				"Spaghetti with Marinara Sauce, and a slice of sourdough bread",				true, 3.89);	}		private void addItem(String name, String description, boolean vegetarian, double price) {		MenuItem menuItem = new MenuItem(name, description, vegetarian, price);		if(numberOfItems >= MAX_ITEMS) {			System.err.println("Sorry, menu is full! Can't add item to menu");		} else {			menuItems[numberOfItems] = menuItem;			numberOfItems = numberOfItems + 1;		}	}				/**	 * 增加了迭代器之后，这个方法就不需要了	 * @return	 */	/*public MenuItem[] getMenuItems() {		return menuItems;	}*/			/**	 * 用来从菜单项数组创建一个DinerMenuIterator,并将它返回给客户	 */	public Iterator createIterator() {		return new DinerMenuIterator(menuItems);	}	}

女招待

 

package dinermerger;/** * 女招待类 * @author wwj * */public class Waitress {	PancakeHouseMenu pancakeHouseMenu;	DinerMenu dinerMenu;		/**	 *在这个构造器中，女招待照顾两个菜单	 * @param pancakeHouseMenu	 * @param dinerMenu	 */	public Waitress(PancakeHouseMenu pancakeHouseMenu, DinerMenu dinerMenu) {		this.pancakeHouseMenu = pancakeHouseMenu;		this.dinerMenu = dinerMenu;	}		public void printMenu() {		Iterator pancakeIterator = pancakeHouseMenu.createIterator();		Iterator dinerIterator = dinerMenu.createIterator();		System.out.println("MENU\n----\nBREAKFAST");		printMenu(pancakeIterator);		System.out.println("\nLUNCH");		printMenu(dinerIterator);	}	private void printMenu(Iterator iterator) {		while(iterator.hasNext()) {	//测试是否还有其他项			MenuItem menuItem = (MenuItem) iterator.next();			System.out.print(menuItem.getName() + ", ");			System.out.print(menuItem.getPrice() + " -- ");			System.out.println(menuItem.getDescription());		}	}}

测试

 

 

package dinermerger;public class MenuTestDrive {	/**	 * @param args	 */	public static void main(String[] args) {		PancakeHouseMenu pancakeHouseMenu = new PancakeHouseMenu();		DinerMenu dinerMenu = new DinerMenu();				Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu);				waitress.printMenu();	}}

结果：

 

MENU

----
BREAKFAST
K&B's Pancake Breakfast, 2.99 -- Pancakes with scrambled eggs, and toast
Regular Pancake Breakfast, 2.99 -- Pancakes with fried eggs, sausage
Blueberry Pancakes, 3.49 -- Pancakes made with fresh blueberries
Waffles, 3.59 -- Waffles, with your choice of blueberries or strawberries
LUNCH
Vegetarian BLT, 2.99 -- (Fakin') Bacon with lettuce & tomato on Whole wheat
BLT, 2.99 -- Bacon with lettuce & tomato on Whole wheat
Soup of the day, 3.29 -- Soup of the day, with a side of potato salad
Hotdog, 3.05 -- A hot dog, with saurkraut, relish, onions, topped with cheese
Steamed Veggies and Brown Rice, 3.99 -- Steamed vegetables over brown rice
Pasta, 3.89 -- Spaghetti with Marinara Sauce, and a slice of sourdough bread

例子2

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利用java.util.Iterator来实现迭代器

提供一个Menu接口，让PancakeHouseMenu和DinerMenu都实现Menu接口，这样Waitress就不用依赖具体的菜单的问题，也不用依赖菜单项的具体实现了。

 

package dinermerger;/** * 这是一个简单的接口，让客户能够取得菜单项 * @author Administrator * */public interface Menu {	public Iterator createIterator();}

DinerMenu

 

 

package dinermerger;import java.util.Iterator;/** * 餐厅菜单 * @author wwj * */public class DinerMenu implements Menu{	static final int MAX_ITEMS = 6;	int numberOfItems = 0;	MenuItem[] menuItems;		//使用一个数组，所以可以控制菜单的长度，并且在取出菜单项的时候，不需要转型			public DinerMenu() {		menuItems = new MenuItem[MAX_ITEMS];		addItem("Vegetarian BLT",				"(Fakin') Bacon with lettuce & tomato on Whole wheat", true,				2.99);		addItem("BLT", "Bacon with lettuce & tomato on Whole wheat", false,				2.99);		addItem("Soup of the day",				"Soup of the day, with a side of potato salad", false, 3.29);		addItem("Hotdog",				"A hot dog, with saurkraut, relish, onions, topped with cheese",				false, 3.05);		addItem("Steamed Veggies and Brown Rice",				"Steamed vegetables over brown rice", true, 3.99);		addItem("Pasta",				"Spaghetti with Marinara Sauce, and a slice of sourdough bread",				true, 3.89);	}		private void addItem(String name, String description, boolean vegetarian, double price) {		MenuItem menuItem = new MenuItem(name, description, vegetarian, price);		if(numberOfItems >= MAX_ITEMS) {			System.err.println("Sorry, menu is full! Can't add item to menu");		} else {			menuItems[numberOfItems] = menuItem;			numberOfItems = numberOfItems + 1;		}	}				/**	 * 增加了迭代器之后，这个方法就不需要了	 * @return	 */	/*public MenuItem[] getMenuItems() {		return menuItems;	}*/			/**	 * 用来从菜单项数组创建一个DinerMenuIterator,并将它返回给客户	 */	public Iterator createIterator() {		return new DinerMenuIterator(menuItems);	}	}

PancakeHouseMenu

 

不创建自己的迭代器，而是调用ArrayList的iterator()方法

 

package dinermerger;import java.util.ArrayList;import java.util.Iterator;/** * 煎饼屋菜单实现 * @author wwj * */public class PancakeHouseMenu implements Menu{	ArrayList menuItems;	public PancakeHouseMenu() {		menuItems = new ArrayList();				addItem("K&B's Pancake Breakfast", "Pancakes with scrambled eggs, and toast", true, 2.99);				addItem("Regular Pancake Breakfast", "Pancakes with fried eggs, sausage", false, 2.99);				addItem("Blueberry Pancakes", "Pancakes made with fresh blueberries", true, 3.49);				addItem("Waffles", "Waffles, with your choice of blueberries or strawberries", true, 3.59);			}		/**	 * 创建一个新的菜单项对象，传入每一个变量，然后将它加入到ArrayList中	 * @param name	菜名	 * @param description 叙述	 * @param vegetarian  是否为素食	 * @param price	价格	 */	public void addItem(String name, String description, boolean vegetarian, double price) {		MenuItem menuItem = new MenuItem(name, description, vegetarian, price);		menuItems.add(menuItem);	}	/*	public ArrayList getMenuItems() {		return menuItems;	}*/			public Iterator createIterator() {		return menuItems.iterator();	}}

DinerMenuIterator

 

 

package dinermerger;import java.util.Iterator;/** * 实现一个具体的迭代器，为餐厅菜单服务 * @author Administrator * */public class DinerMenuIterator implements Iterator {	MenuItem[] items;	int position = 0;	//记录当前数组遍历的位置		public DinerMenuIterator(MenuItem[] items) {		this.items = items;	}	@Override	public boolean hasNext() {		if(position >= items.length || items[position] == null) {			return false;		} else {			return true;		}	}	@Override	public Object next() {		MenuItem menuItem = items[position];		position = position + 1;		return menuItem;	}	@Override	public void remove() {		if(position <= 0) {			throw new IllegalStateException("You can't remove an item until you've done at least on next()");		}		if(items[position - 1] != null) {			for(int i = position - 1; i < (items.length - 1); i++) {				items[i] = items[i + 1];			}			items[items.length - 1] = null;		}			}}

Waitress

 

 

package dinermerger;import java.util.Iterator; /** * 女招待类 * @author wwj * */public class Waitress {//	PancakeHouseMenu pancakeHouseMenu;//	DinerMenu dinerMenu;	Menu pancakeHouseMenu;	Menu dinerMenu;		/**	 *在这个构造器中，女招待照顾两个菜单	 * @param pancakeHouseMenu	 * @param dinerMenu	 */	public Waitress(Menu pancakeHouseMenu, Menu dinerMenu) {		this.pancakeHouseMenu = pancakeHouseMenu;		this.dinerMenu = dinerMenu;	}		public void printMenu() {		Iterator pancakeIterator = pancakeHouseMenu.createIterator();		Iterator dinerIterator = dinerMenu.createIterator();		System.out.println("MENU\n----\nBREAKFAST");		printMenu(pancakeIterator);		System.out.println("\nLUNCH");		printMenu(dinerIterator);	}	private void printMenu(Iterator iterator) {		while(iterator.hasNext()) {	//测试是否还有其他项			MenuItem menuItem = (MenuItem) iterator.next();			System.out.print(menuItem.getName() + ", ");			System.out.print(menuItem.getPrice() + " -- ");			System.out.println(menuItem.getDescription());		}	}}

 

增加一个CafeMenu会变成以下这样

 

package dinermerger;import java.util.Hashtable;import java.util.Iterator;/** * 咖啡厅菜单 * @author wwj * */public class CafeMenu implements Menu{	Hashtable menuItems = new Hashtable();		public CafeMenu() {		addItem("Veggie Burger and Air Fries",				"Veggie burger on a whole wheat bun, lettuce, tomato, and fries",				true, 3.99);		addItem("Soup of the day",				"A cup of the soup of the day, with a side salad", false, 3.69);		addItem("Burrito",				"A large burrito, with whole pinto beans, salsa, guacamole",				true, 4.29);	}			public void addItem(String name, String description, boolean vegetarian, double price) {		MenuItem menuItem = new MenuItem(name, description, vegetarian, price);		menuItems.put(menuItem.getName(), menuItem);	}	@Override	public Iterator createIterator() {		return menuItems.values().iterator();	}}

 

 

package dinermerger;import java.util.Iterator; /** * 女招待类 * @author wwj * */public class Waitress {//	PancakeHouseMenu pancakeHouseMenu;//	DinerMenu dinerMenu;	Menu pancakeHouseMenu;	Menu dinerMenu;	Menu cafeMenu;			/**	 *在这个构造器中，女招待照顾两个菜单	 * @param pancakeHouseMenu	 * @param dinerMenu	 */	public Waitress(Menu pancakeHouseMenu, Menu dinerMenu) {		this.pancakeHouseMenu = pancakeHouseMenu;		this.dinerMenu = dinerMenu;	}		/**	 * 新增一个cafeMenu	 * @param pancakeHouseMenu	 * @param dinerMenu	 * @param cafeMenu	 */	public Waitress(Menu pancakeHouseMenu, Menu dinerMenu, Menu cafeMenu) {		this.pancakeHouseMenu = pancakeHouseMenu;		this.dinerMenu = dinerMenu;		this.cafeMenu = cafeMenu;	}	public void printMenu() {		Iterator pancakeIterator = pancakeHouseMenu.createIterator();		Iterator dinerIterator = dinerMenu.createIterator();		Iterator cafeIterator = cafeMenu.createIterator();		System.out.println("MENU\n----\nBREAKFAST");		printMenu(pancakeIterator);		System.out.println("\nLUNCH");		printMenu(dinerIterator);		System.out.println("\nDINNER");		printMenu(cafeIterator);	}	private void printMenu(Iterator iterator) {		while(iterator.hasNext()) {	//测试是否还有其他项			MenuItem menuItem = (MenuItem) iterator.next();			System.out.print(menuItem.getName() + ", ");			System.out.print(menuItem.getPrice() + " -- ");			System.out.println(menuItem.getDescription());		}	}}

Test

 

package dinermerger;public class MenuTestDrive {	/**	 * @param args	 */	public static void main(String[] args) {//		PancakeHouseMenu pancakeHouseMenu = new PancakeHouseMenu();//		DinerMenu dinerMenu = new DinerMenu();//		//		Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu);//		//		waitress.printMenu();				Menu pancakeHouseMenu = new PancakeHouseMenu();		Menu dinerMenu = new DinerMenu();		Menu cafeMenu = new CafeMenu();				Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu, cafeMenu);		waitress.printMenu();	}}

结果：

 

MENU

----
BREAKFAST
K&B's Pancake Breakfast, 2.99 -- Pancakes with scrambled eggs, and toast
Regular Pancake Breakfast, 2.99 -- Pancakes with fried eggs, sausage
Blueberry Pancakes, 3.49 -- Pancakes made with fresh blueberries
Waffles, 3.59 -- Waffles, with your choice of blueberries or strawberries
LUNCH
Vegetarian BLT, 2.99 -- (Fakin') Bacon with lettuce & tomato on Whole wheat
BLT, 2.99 -- Bacon with lettuce & tomato on Whole wheat
Soup of the day, 3.29 -- Soup of the day, with a side of potato salad
Hotdog, 3.05 -- A hot dog, with saurkraut, relish, onions, topped with cheese
Steamed Veggies and Brown Rice, 3.99 -- Steamed vegetables over brown rice
Pasta, 3.89 -- Spaghetti with Marinara Sauce, and a slice of sourdough bread
DINNER
Soup of the day, 3.69 -- A cup of the soup of the day, with a side salad
Burrito, 4.29 -- A large burrito, with whole pinto beans, salsa, guacamole
Veggie Burger and Air Fries, 3.99 -- Veggie burger on a whole wheat bun, lettuce, tomato, and fries

为了让女招待更加有扩展性，我们这样做

 

package dinermerger;import java.util.ArrayList;import java.util.Iterator; /** * 女招待类 * @author wwj * */public class Waitress {//	PancakeHouseMenu pancakeHouseMenu;//	DinerMenu dinerMenu;//	Menu pancakeHouseMenu;//	Menu dinerMenu;//	Menu cafeMenu;		ArrayList menus;	/*	*//**	 *在这个构造器中，女招待照顾两个菜单	 * @param pancakeHouseMenu	 * @param dinerMenu	 *//*	public Waitress(Menu pancakeHouseMenu, Menu dinerMenu) {		this.pancakeHouseMenu = pancakeHouseMenu;		this.dinerMenu = dinerMenu;	}		*//**	 * 新增一个cafeMenu	 * @param pancakeHouseMenu	 * @param dinerMenu	 * @param cafeMenu	 *//*	public Waitress(Menu pancakeHouseMenu, Menu dinerMenu, Menu cafeMenu) {		this.pancakeHouseMenu = pancakeHouseMenu;		this.dinerMenu = dinerMenu;		this.cafeMenu = cafeMenu;	}*/	public Waitress(ArrayList menus) {		this.menus = menus;	}	public void printMenu() {/*		Iterator pancakeIterator = pancakeHouseMenu.createIterator();		Iterator dinerIterator = dinerMenu.createIterator();		Iterator cafeIterator = cafeMenu.createIterator();		System.out.println("MENU\n----\nBREAKFAST");		printMenu(pancakeIterator);		System.out.println("\nLUNCH");		printMenu(dinerIterator);		System.out.println("\nDINNER");		printMenu(cafeIterator);*/		Iterator menuIterator = menus.iterator();		while(menuIterator.hasNext()) {			Menu menu = (Menu)menuIterator.next();			printMenu(menu.createIterator());		}			}		private void printMenu(Iterator iterator) {		while(iterator.hasNext()) {	//测试是否还有其他项			MenuItem menuItem = (MenuItem) iterator.next();			System.out.print(menuItem.getName() + ", ");			System.out.print(menuItem.getPrice() + " -- ");			System.out.println(menuItem.getDescription());		}	}}

测试的时候我们就可以这样

 

 

package dinermerger;import java.util.ArrayList;public class MenuTestDrive {	/**	 * @param args	 */	public static void main(String[] args) {//		PancakeHouseMenu pancakeHouseMenu = new PancakeHouseMenu();//		DinerMenu dinerMenu = new DinerMenu();//		//		Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu);//		//		waitress.printMenu();				Menu pancakeHouseMenu = new PancakeHouseMenu();		Menu dinerMenu = new DinerMenu();		Menu cafeMenu = new CafeMenu();		//		Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu, cafeMenu);		ArrayList menus = new ArrayList();		menus.add(pancakeHouseMenu);		menus.add(dinerMenu);		menus.add(cafeMenu);		Waitress waitress = new Waitress(menus);		waitress.printMenu();	}}

 

总算是要讲到组合模式了，这个模式可以解决迭代器模式中不能解决的一个难题。比如我们需要一个新的餐单，菜单下又有子菜单，单单用迭代器就不能解决了。这时候可以考虑到用树形结构来展示整个菜单。

看下面的例子吧：

定义菜单组件

 

package composite;/** * 定义菜单组件 * @author Administrator * */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();	}}

 

实现菜单 

package composite;import java.util.ArrayList;import java.util.Iterator;public class Menu extends MenuComponent{	ArrayList menuComponents = new ArrayList();	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("------------------");				Iterator iterator = menuComponents.iterator();		while(iterator.hasNext()) {			MenuComponent menuComponent =				(MenuComponent) iterator.next();			menuComponent.print();		}	}}

实现菜单项

 

package composite;/** * 实现菜单项 * @author Administrator * */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 boolean isVegetarian() {		return vegetarian;	}	public double getPrice() {		return price;	}			public void print(){		System.out.print("  " + getName());		if(isVegetarian()) {			System.out.print("(v)");		}		System.out.println("," + getPrice());		System.out.println("    --" + getDescription());	}		}

 

变得十分快乐的女招待

 

package composite;import java.util.Iterator;  public class Waitress {	MenuComponent allMenus; 	public Waitress(MenuComponent allMenus) {		this.allMenus = allMenus;	} 	public void printMenu() {		allMenus.print();	}}

我们这样测试

 

 

package composite;import java.util.*;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));		pancakeHouseMenu.add(new MenuItem(			"Regular Pancake Breakfast", 			"Pancakes with fried eggs, sausage", 			false,			2.99));		pancakeHouseMenu.add(new MenuItem(			"Blueberry Pancakes",			"Pancakes made with fresh blueberries, and blueberry syrup",			true,			3.49));		pancakeHouseMenu.add(new MenuItem(			"Waffles",			"Waffles, with your choice of blueberries or strawberries",			true,			3.59));		dinerMenu.add(new MenuItem(			"Vegetarian BLT",			"(Fakin') Bacon with lettuce & tomato on whole wheat", 			true, 			2.99));		dinerMenu.add(new MenuItem(			"BLT",			"Bacon with lettuce & tomato on whole wheat", 			false, 			2.99));		dinerMenu.add(new MenuItem(			"Soup of the day",			"A bowl of the soup of the day, with a side of potato salad", 			false, 			3.29));		dinerMenu.add(new MenuItem(			"Hotdog",			"A hot dog, with saurkraut, relish, onions, topped with cheese",			false, 			3.05));		dinerMenu.add(new MenuItem(			"Steamed Veggies and Brown Rice",			"Steamed vegetables over brown rice", 			true, 			3.99)); 		dinerMenu.add(new MenuItem(			"Pasta",			"Spaghetti with Marinara Sauce, and a slice of sourdough bread",			true, 			3.89));   		dinerMenu.add(dessertMenu);  		dessertMenu.add(new MenuItem(			"Apple Pie",			"Apple pie with a flakey crust, topped with vanilla icecream",			true,			1.59));  		dessertMenu.add(new MenuItem(			"Cheesecake",			"Creamy New York cheesecake, with a chocolate graham crust",			true,			1.99));		dessertMenu.add(new MenuItem(			"Sorbet",			"A scoop of raspberry and a scoop of lime",			true,			1.89));		cafeMenu.add(new MenuItem(			"Veggie Burger and Air Fries",			"Veggie burger on a whole wheat bun, lettuce, tomato, and fries",			true, 			3.99));		cafeMenu.add(new MenuItem(			"Soup of the day",			"A cup of the soup of the day, with a side salad",			false, 			3.69));		cafeMenu.add(new MenuItem(			"Burrito",			"A large burrito, with whole pinto beans, salsa, guacamole",			true, 			4.29));		cafeMenu.add(coffeeMenu);		coffeeMenu.add(new MenuItem(			"Coffee Cake",			"Crumbly cake topped with cinnamon and walnuts",			true,			1.59));		coffeeMenu.add(new MenuItem(			"Bagel",			"Flavors include sesame, poppyseed, cinnamon raisin, pumpkin",			false,			0.69));		coffeeMenu.add(new MenuItem(			"Biscotti",			"Three almond or hazelnut biscotti cookies",			true,			0.89)); 		Waitress waitress = new Waitress(allMenus);   		waitress.printMenu();	}}

 

测试结果：

ALL MENUS, All menus combined
------------------
PANCAKE HOUSE MENU, Breakfast
------------------
  K&B's Pancake Breakfast(v),2.99
    --Pancakes with scrambled eggs, and toast
  Regular Pancake Breakfast,2.99
    --Pancakes with fried eggs, sausage
  Blueberry Pancakes(v),3.49
    --Pancakes made with fresh blueberries, and blueberry syrup
  Waffles(v),3.59
    --Waffles, with your choice of blueberries or strawberries
DINER MENU, Lunch
------------------
  Vegetarian BLT(v),2.99
    --(Fakin') Bacon with lettuce & tomato on whole wheat
  BLT,2.99
    --Bacon with lettuce & tomato on whole wheat
  Soup of the day,3.29
    --A bowl of the soup of the day, with a side of potato salad
  Hotdog,3.05
    --A hot dog, with saurkraut, relish, onions, topped with cheese
  Steamed Veggies and Brown Rice(v),3.99
    --Steamed vegetables over brown rice
  Pasta(v),3.89
    --Spaghetti with Marinara Sauce, and a slice of sourdough bread
DESSERT MENU, Dessert of course!
------------------
  Apple Pie(v),1.59
    --Apple pie with a flakey crust, topped with vanilla icecream
  Cheesecake(v),1.99
    --Creamy New York cheesecake, with a chocolate graham crust
  Sorbet(v),1.89
    --A scoop of raspberry and a scoop of lime
CAFE MENU, Dinner
------------------
  Veggie Burger and Air Fries(v),3.99
    --Veggie burger on a whole wheat bun, lettuce, tomato, and fries
  Soup of the day,3.69
    --A cup of the soup of the day, with a side salad
  Burrito(v),4.29
    --A large burrito, with whole pinto beans, salsa, guacamole
COFFEE MENU, Stuff to go with your afternoon coffee
------------------
  Coffee Cake(v),1.59
    --Crumbly cake topped with cinnamon and walnuts
  Bagel,0.69
    --Flavors include sesame, poppyseed, cinnamon raisin, pumpkin
  Biscotti(v),0.89
    --Three almond or hazelnut biscotti cookies

 

转载于:https://www.cnblogs.com/xinyuyuanm/p/3177778.html

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