迭代器模式

/**
 * 菜单
 */
public class Menu {
   private String name;
   private Double price;

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

    public String getName() {
        return name;
    }

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

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }
}

/**
 * 晚餐店
 */
public class DinnerShop {

    private static final int MAX_ITEMS = 4;
    int index = 0;
    Menu[] menuItems;

    public DinnerShop() {
        menuItems = new Menu[MAX_ITEMS];

        // 默认就放入菜单项
        addItem("浪漫晚餐", 299d);
        addItem("小龙虾", 99d);
        addItem("鱿鱼", 49d);
        addItem("扇贝", 89d);
    }

    public void addItem(String name, double price) {
        Menu menu = new Menu(name, price);
        if (index >= MAX_ITEMS) {
            System.err.println("对不起, 菜单页满了");
        } else {
            menuItems[index] = menu;
            index++;
        }
    }

    // 创建迭代器：重点
    public Iterator createIteraotr() {
        return new DinnerMenuIterator(menuItems);
    }
}

/**
 * 晚餐菜单遍历类
 */
public class DinnerMenuIterator implements Iterator {
    Menu[] menuItems;
    int position = 0;

    public DinnerMenuIterator(Menu[] menuItems) {
        this.menuItems = menuItems;
    }

    @Override
    public boolean hasNext() {
        if (position >= menuItems.length || menuItems[position] == null) {
            return false;
        }

        return true;
    }

    @Override
    public Object next() {
        Menu menuItem = menuItems[position];
        position++;
        return menuItem;
    }
}

/**
 * 汉堡店菜单
 */
public class PancakeHouseShop {

    /**
     * 菜单列表
     */
    List<Menu> menuItems;

    public PancakeHouseShop() {
        this.menuItems = new ArrayList<>();

        // 默认就放入菜单项
        addItem("可乐", 3d);
        addItem("汉堡", 13d);
        addItem("薯条", 8d);
        addItem("鸡翅", 5d);
    }

    public void addItem(String name, Double price) {
        Menu menu = new Menu(name, price);
        menuItems.add(menu);
    }

    // 产生迭代器
    public Iterator createIterator() {
        return new PancakeHouseMenuIterator(menuItems);
    }
}

/**
 * 汉堡包菜单迭代类
 */
public class PancakeHouseMenuIterator implements Iterator {
    List<Menu> menuItems;
    int position = 0;

    public PancakeHouseMenuIterator(List<Menu> menuItems) {
        this.menuItems = menuItems;
    }

    @Override
    public boolean hasNext() {
        if (position >= menuItems.size() || menuItems.get(position) == null) {
            return false;
        }

        return true;
    }

    @Override
    public Object next() {
        Menu menuItem = menuItems.get(position);
        position++;

        return menuItem;
    }
}

/**
 * 服务生
 */
public class Waiter {

    public void print() {
        System.out.println("================== 汉堡包菜单 ======================");
        PancakeHouseShop pancakeHouseShop = new PancakeHouseShop();
        Iterator pancakeHouseMenuIterator = pancakeHouseShop.createIterator();
        printMenu(pancakeHouseMenuIterator);

        System.out.println("=================== 晚餐菜单 =====================");
        DinnerShop dinnerShop = new DinnerShop();
        Iterator dinnerMenuIterator = dinnerShop.createIteraotr();
        printMenu(dinnerMenuIterator);
    }

    private void printMenu(Iterator iterator) {
        while (iterator.hasNext()) {
            Menu menu = (Menu) iterator.next();
            System.out.println("名称: " + menu.getName() + "======== 价格: " + menu.getPrice());
        }
    }

    public static void main(String[] args) {
        Waiter waiter = new Waiter();
        waiter.print();
    }
}控制台打印：
================== 汉堡包菜单 ======================名称: 可乐======== 价格: 3.0名称: 汉堡======== 价格: 13.0名称: 薯条======== 价格: 8.0名称: 鸡翅======== 价格: 5.0=================== 晚餐菜单 =====================名称: 浪漫晚餐======== 价格: 299.0名称: 小龙虾======== 价格: 99.0名称: 鱿鱼======== 价格: 49.0名称: 扇贝======== 价格: 89.0