一、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。

二、举例

合并一个餐厅菜单和煎饼屋菜单，要求如下

餐厅菜单用数组存储菜单项
煎饼屋用ArrayList存储菜单项
女服务员需要遍历餐馆的所有菜单

自定义迭代器

迭代器接口类

package com.jackeys.IteratorMode.DIY;/*** @Description: 迭代器接口* @ClassName: Iterator* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:40* @Version: 1.0*/
public interface Iterator {boolean hasNext();Object next();
}

菜单项类

package com.jackeys.IteratorMode.DIY;/*** @Description: 菜单项类* @ClassName: MenuItem* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:35* @Version: 1.0*/
public class MenuItem {/*** 菜名*/private String name;/*** 描述*/private String description;/*** 是否为素食*/private boolean vegetarian;/*** 价格*/private 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 void setName(String name) {this.name = name;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}public boolean isVegetarian() {return vegetarian;}public void setVegetarian(boolean vegetarian) {this.vegetarian = vegetarian;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}
}

餐厅菜单类

package com.jackeys.IteratorMode.DIY;/*** @Description: 餐厅菜单类* @ClassName: DinerMenu* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:03* @Version: 1.0*/
public class DinerMenu {private static final int MAX_ITEMS = 6;private int numberOfItem = 0;private MenuItem[] menuItems;public DinerMenu() {this.menuItems = new MenuItem[MAX_ITEMS];this.addItem("战斧牛排","威武霸气的战斧配上鲜嫩多汁的牛排",false, 39.99);this.addItem("蜜汁手扒饭", "采用蜜汁酱料，手工拌饭",false, 19.99);this.addItem("例汤", "蔬菜例汤，爽口", true, 10.99);this.addItem("香辣鸡腿","鲜肥多汁，香酥脆口", false, 15.99);}/*** @MethodName: addItem* @Description: 添加菜单项* @Param name* @Param description* @Param vegetarian* @Param price* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 8:08* @Version: 1.0*/public void addItem(String name, String description, boolean vegetarian, double price) {MenuItem menuItem = new MenuItem(name, description, vegetarian, price);if (this.numberOfItem >= MAX_ITEMS) {System.out.println("很抱歉，餐厅菜单已满");} else {this.menuItems[this.numberOfItem] = menuItem;this.numberOfItem++;}}public Iterator createIterator() {return new DinerMenuIterator(this.menuItems);}
}

餐厅迭代器类

package com.jackeys.IteratorMode.DIY;/*** @Description: 餐厅迭代器类* @ClassName: DinerMenuIterator* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:43* @Version: 1.0*/
public class DinerMenuIterator implements Iterator {private MenuItem[] items;private int position = 0;public DinerMenuIterator(MenuItem [] items) {this.items = items;}@Overridepublic boolean hasNext() {if (this.position >= this.items.length || this.items[position] == null) {return false;}return true;}@Overridepublic Object next() {MenuItem menuItem = this.items[this.position];this.position++;return menuItem;}
}

煎饼屋菜单类

package com.jackeys.IteratorMode.DIY;import java.util.ArrayList;
import java.util.Arrays;/*** @Description: 煎饼屋菜单类* @ClassName: PancakeHouseMenu* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:48* @Version: 1.0*/
public class PancakeHouseMenu {private ArrayList<MenuItem> menuItems;public PancakeHouseMenu() {this.menuItems = new ArrayList<>();this.addItem("特色煎饼", "本店特色煎饼，不好吃不要钱",true, 5.99d);this.addItem("麻辣煎饼", "又麻又辣，太上头", true, 4.99d);this.addItem("田园煎饼", "新鲜甘甜，健康美味",true, 4.99d);this.addItem("肉丝煎饼","大口煎饼，大份满足",false,6.99d);}/*** @MethodName: addItem* @Description: 添加菜单项* @Param name* @Param description* @Param vegetarian* @Param price* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 7:51* @Version: 1.0*/public void addItem(String name, String description, boolean vegetarian, double price) {MenuItem menuItem = new MenuItem(name, description, vegetarian, price);this.menuItems.add(menuItem);}public Iterator createIterator() {return new PancakeHouseMenuIterator(this.menuItems);}
}

煎饼屋迭代器类

package com.jackeys.IteratorMode.DIY;import java.util.ArrayList;/*** @Description: 煎饼屋迭代器* @ClassName: PancakeHouseMenuIterator* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:58* @Version: 1.0*/
public class PancakeHouseMenuIterator implements Iterator {private ArrayList<MenuItem> items;private int position = 1;public PancakeHouseMenuIterator(ArrayList<MenuItem> items) {this.items = items;}@Overridepublic boolean hasNext() {if (this.position >= this.items.size() || this.items.get(this.position) == null) {return false;}return true;}@Overridepublic Object next() {MenuItem menuItem = this.items.get(this.position);this.position++;return menuItem;}
}

女服务员类

package com.jackeys.IteratorMode.DIY;/*** @Description: 女服务员* @ClassName: Waitress* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:15* @Version: 1.0*/
public class Waitress {/*** 煎饼屋菜单*/private PancakeHouseMenu pancakeHouseMenu;/*** 餐厅菜单*/private DinerMenu dinerMenu;public Waitress(PancakeHouseMenu pancakeHouseMenu, DinerMenu dinerMenu) {this.pancakeHouseMenu = pancakeHouseMenu;this.dinerMenu = dinerMenu;}/*** @MethodName: printMenu* @Description: 打印菜单* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 8:19* @Version: 1.0*/public void printMenu() {Iterator pancakeHouseIterator = this.pancakeHouseMenu.createIterator();Iterator dinerMenuIterator = this.dinerMenu.createIterator();System.out.println("==================煎饼屋菜单================");this.printMenu(pancakeHouseIterator);System.out.println("==================餐厅菜单================");this.printMenu(dinerMenuIterator);}public void printMenu(Iterator iterator) {while (iterator.hasNext()) {MenuItem menuItem = (MenuItem) iterator.next();System.out.println("菜名：" + menuItem.getName() + "\n" + "描述：" + menuItem.getDescription() + "\n" + "是否为素食：" + menuItem.isVegetarian() + "\n" + "价格：" + menuItem.getPrice() + "元");}}}

测试

package com.jackeys.IteratorMode.DIY;/*** @Description: 测试迭代器模式* @ClassName: Test* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:26* @Version: 1.0*/
public class Test {public static void main(String[] args) {PancakeHouseMenu pancakeHouseMenu = new PancakeHouseMenu();DinerMenu dinerMenu = new DinerMenu();Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu);waitress.printMenu();}
}

运行截图

Java内置迭代器

菜单接口类

package com.jackeys.IteratorMode.JavaInner;import java.util.Iterator;/*** @Description: 菜单接口类* @ClassName: Menu* @Package com.jackeys.IteratorMode.JavaInner* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:37* @Version: 1.0*/
public interface Menu {Iterator createIterator();
}

餐厅菜单类

package com.jackeys.IteratorMode.JavaInner;import com.jackeys.IteratorMode.JavaInner.DinerMenuIterator;
import com.jackeys.IteratorMode.JavaInner.MenuItem;import java.util.Iterator;/*** @Description: 餐厅菜单类* @ClassName: DinerMenu* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:03* @Version: 1.0*/
public class DinerMenu implements Menu{private static final int MAX_ITEMS = 6;private int numberOfItem = 0;private MenuItem[] menuItems;public DinerMenu() {this.menuItems = new MenuItem[MAX_ITEMS];this.addItem("战斧牛排","威武霸气的战斧配上鲜嫩多汁的牛排",false, 39.99);this.addItem("蜜汁手扒饭", "采用蜜汁酱料，手工拌饭",false, 19.99);this.addItem("例汤", "蔬菜例汤，爽口", true, 10.99);this.addItem("香辣鸡腿","鲜肥多汁，香酥脆口", false, 15.99);}/*** @MethodName: addItem* @Description: 添加菜单项* @Param name* @Param description* @Param vegetarian* @Param price* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 8:08* @Version: 1.0*/public void addItem(String name, String description, boolean vegetarian, double price) {MenuItem menuItem = new MenuItem(name, description, vegetarian, price);if (this.numberOfItem >= MAX_ITEMS) {System.out.println("很抱歉，餐厅菜单已满");} else {this.menuItems[this.numberOfItem] = menuItem;this.numberOfItem++;}}@Overridepublic Iterator createIterator() {return new DinerMenuIterator(this.menuItems);}
}

餐厅迭代器类

package com.jackeys.IteratorMode.JavaInner;import com.jackeys.IteratorMode.JavaInner.MenuItem;import java.util.Iterator;/*** @Description: 餐厅迭代器类* @ClassName: DinerMenuIterator* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:43* @Version: 1.0*/
public class DinerMenuIterator implements Iterator {private MenuItem[] items;private int position = 0;public DinerMenuIterator(MenuItem [] items) {this.items = items;}@Overridepublic boolean hasNext() {if (this.position >= this.items.length || this.items[position] == null) {return false;}return true;}@Overridepublic Object next() {MenuItem menuItem = this.items[this.position];this.position++;return menuItem;}
}

咖啡菜单类

package com.jackeys.IteratorMode.JavaInner;import java.util.Hashtable;
import java.util.Iterator;/*** @Description: 咖啡菜单* @ClassName: CafeMenu* @Package com.jackeys.IteratorMode.JavaInner* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:40* @Version: 1.0*/
public class CafeMenu implements Menu{private Hashtable<String, MenuItem> menuItems;public CafeMenu() {this.menuItems = new Hashtable<>();this.addItem("现磨咖啡","新鲜的味道",true,9.99d);this.addItem("意大利咖啡","来自意大利的风味",true,8.99d);this.addItem("浓缩咖啡","快速冲泡",true,5.99d);this.addItem("猫屎咖啡","高贵美味",true,10.99d);}/*** @MethodName: addItem* @Description: 添加菜单项* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 8:43* @Version: 1.0*/public void addItem(String name, String description, boolean vegetarian, double price) {MenuItem menuItem = new MenuItem(name, description, vegetarian, price);this.menuItems.put(menuItem.getName(), menuItem);}@Overridepublic Iterator createIterator() {return this.menuItems.values().iterator();}
}

煎饼屋菜单类

package com.jackeys.IteratorMode.JavaInner;import com.jackeys.IteratorMode.JavaInner.MenuItem;import java.util.ArrayList;
import java.util.Iterator;/*** @Description: 煎饼屋菜单类* @ClassName: PancakeHouseMenu* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 7:48* @Version: 1.0*/
public class PancakeHouseMenu implements Menu{private ArrayList<MenuItem> menuItems;public PancakeHouseMenu() {this.menuItems = new ArrayList<>();this.addItem("特色煎饼", "本店特色煎饼，不好吃不要钱",true, 5.99d);this.addItem("麻辣煎饼", "又麻又辣，太上头", true, 4.99d);this.addItem("田园煎饼", "新鲜甘甜，健康美味",true, 4.99d);this.addItem("肉丝煎饼","大口煎饼，大份满足",false,6.99d);}/*** @MethodName: addItem* @Description: 添加菜单项* @Param name* @Param description* @Param vegetarian* @Param price* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 7:51* @Version: 1.0*/public void addItem(String name, String description, boolean vegetarian, double price) {MenuItem menuItem = new MenuItem(name, description, vegetarian, price);this.menuItems.add(menuItem);}@Overridepublic Iterator createIterator() {return this.menuItems.iterator();}
}

女服务员类

package com.jackeys.IteratorMode.JavaInner;import java.util.Iterator;/*** @Description: 女服务员* @ClassName: Waitress* @Package com.jackeys.IteratorMode.DIY* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:15* @Version: 1.0*/
public class Waitress {/*** 煎饼屋菜单*/private Menu pancakeHouseMenu;/*** 餐厅菜单*/private Menu dinerMenu;/*** 咖啡菜单*/private Menu cafeMenu;public Waitress(Menu pancakeHouseMenu,Menu dinerMenu, Menu cafeMenu) {this.pancakeHouseMenu = pancakeHouseMenu;this.dinerMenu = dinerMenu;this.cafeMenu = cafeMenu;}/*** @MethodName: printMenu* @Description: 打印菜单* @Return void* @Auther: Jackeys 1623427947@qq.com* @Date: 2021/10/24 8:19* @Version: 1.0*/public void printMenu() {Iterator pancakeHouseIterator = this.pancakeHouseMenu.createIterator();Iterator dinerMenuIterator = this.dinerMenu.createIterator();Iterator cafeMenuIterator = this.cafeMenu.createIterator();System.out.println("==================煎饼屋菜单（早餐）================");this.printMenu(pancakeHouseIterator);System.out.println("==================餐厅菜单（中餐）================");this.printMenu(dinerMenuIterator);System.out.println("==================咖啡菜单（晚餐）================");this.printMenu(cafeMenuIterator);}public void printMenu(Iterator iterator) {while (iterator.hasNext()) {MenuItem menuItem = (MenuItem) iterator.next();System.out.println("菜名：" + menuItem.getName() + "\n" + "描述：" + menuItem.getDescription() + "\n" + "是否为素食：" + menuItem.isVegetarian() + "\n" + "价格：" + menuItem.getPrice()+ "元");System.out.println("------------------------------------");}}}

测试

package com.jackeys.IteratorMode.JavaInner;/*** @Description: 测试JAVA内置Iterator* @ClassName: Test* @Package com.jackeys.IteratorMode.JavaInner* @Author: Jackeys 1623427047@qq.com* @Copyright 版权归Jackeys企业（或个人）所有* @CreateTime: 2021/10/24 8:49* @Version: 1.0*/
public class Test {public static void main(String[] args) {Menu cafeMenu = new CafeMenu();Menu dinerMenu = new DinerMenu();Menu pancakeHouseMenu = new PancakeHouseMenu();Waitress waitress = new Waitress(pancakeHouseMenu, dinerMenu, cafeMenu);waitress.printMenu();}
}

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你知道迭代器模式吗？

迭代器模式

一、迭代器模式

二、举例

自定义迭代器

Java内置迭代器

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