Java设计模式 - 迭代器模式

桃扇骨 2023-03-06 05:45 86阅读 0赞

**目录**

迭代器模式：

迭代器优点：

迭代器模式应用：

迭代器实例：

上述代码 GitHub 地址：https://github.com/baicun/designPatterns

--------------------

# [迭代器模式：][Link 1] #

提供一种方法顺序访问一个聚合对象中的各个对象

# [迭代器优点：][Link 2] #

耦合度低，灵活

# [迭代器模式应用：][Link 3] #

Java内置迭代器

# [迭代器实例：][Link 4] #

类图：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NzZG5fMDkxMQ_size_16_color_FFFFFF_t_70][]

示例：俩家不同的餐馆合并，需要打印出不同组合的菜单，面包馆呢是遍历的集合，而小饭馆呢是遍历的数组，所以需要找一个统一的方法，来解决这个问题，这里使用迭代器模式设计。

代码：

面包馆-CakeHouseMenu.java

public class CakeHouseMenu {
    	private ArrayList<MenuItem> menuItems;
    	
    	
    	public CakeHouseMenu() {
    		menuItems = new ArrayList<MenuItem>();
    		
    		addItem("KFC Cake Breakfast","boiled eggs&toast&cabbage",true,3.99f);
    		addItem("MDL Cake Breakfast","fried eggs&toast",false,3.59f);
    		addItem("Stawberry Cake","fresh stawberry",true,3.29f);
    		addItem("Regular Cake Breakfast","toast&sausage",true,2.59f);
    	}
    
    	private void addItem(String name, String description, boolean vegetable,
    			float price) {
    		MenuItem menuItem = new MenuItem(name, description, vegetable, price);
    		menuItems.add(menuItem);
    	}
    
    
    	
    	public Iterator getIterator()
    	{
    		return new CakeHouseIterator() ;
    	}
    
    	class CakeHouseIterator implements  Iterator
    	 {
    		private int position=0;
    		public CakeHouseIterator()
    		{
    			  position=0;
    		}
    
    		 	@Override
    			public boolean hasNext() {
    			// TODO Auto-generated method stub
    			if(position<menuItems.size())
    			{
    				return true;
    			}
    
    			return false;
    		}
    
    		@Override
    		public Object next() {
    			// TODO Auto-generated method stub
    			MenuItem menuItem =menuItems.get(position);
    			position++;
    			return menuItem;
    		}};
    	//其他功能代码
    
    }

小餐馆-DinerMenu.java

public class DinerMenu {
    	private final static int Max_Items = 5;
    	private int numberOfItems = 0;
    	private MenuItem[] menuItems;
    
    	public DinerMenu() {
    		menuItems = new MenuItem[Max_Items];
    		addItem("vegetable Blt", "bacon&lettuce&tomato&cabbage", true, 3.58f);
    		addItem("Blt", "bacon&lettuce&tomato", false, 3.00f);
    		addItem("bean soup", "bean&potato salad", true, 3.28f);
    		addItem("hotdog", "onions&cheese&bread", false, 3.05f);
    
    	}
    
    	private void addItem(String name, String description, boolean vegetable,
    			float price) {
    		MenuItem menuItem = new MenuItem(name, description, vegetable, price);
    		if (numberOfItems >= Max_Items) {
    			System.err.println("sorry,menu is full!can not add another item");
    		} else {
    			menuItems[numberOfItems] = menuItem;
    			numberOfItems++;
    		}
    
    	}
    
    	public Iterator getIterator() {
    		return new DinerIterator();
    	}
    
    	class DinerIterator implements Iterator {
    		private int position;
    
    		public DinerIterator() {
    			position = 0;
    		}
    
    		@Override
    		public boolean hasNext() {
    			// TODO Auto-generated method stub
    			if (position < numberOfItems) {
    				return true;
    			}
    			
    			return false;
    		}
    
    		@Override
    		public Object next() {
    			// TODO Auto-generated method stub
    			MenuItem menuItem = menuItems[position];
    			position++;
    			return menuItem;
    		}
    	};
    }

迭代器接口-Iterator.java

public interface Iterator {
    	
    	public boolean hasNext();
    	public Object next();
    }

打印菜单功能-Waitress.java

public class Waitress {
    	private ArrayList<Iterator> iterators=new ArrayList<Iterator>();
    
    
    	public Waitress() {
    		
    	}
    	public void addIterator(Iterator iterator)
    	{
    		iterators.add(iterator);
    		
    	}
    	public void printMenu() {
    		Iterator iterator;
    		MenuItem menuItem;
    		for (int i = 0, len = iterators.size(); i < len; i++) {
    			iterator = iterators.get(i);
    			
    			while(iterator.hasNext())
    			{
    				menuItem=(MenuItem)	iterator.next();
    				System.out.println(menuItem.getName() + "***"
    						+menuItem.getPrice()+"***"+ menuItem.getDescription());
    			}
    		}
    	}
    }

测试类：

public class MainTest {
    	public static void main(String[] args) {
    		Waitress mWaitress=new Waitress();
    		CakeHouseMenu mCakeHouseMenu = new CakeHouseMenu();
    		DinerMenu	mDinerMenu = new DinerMenu();
    		mWaitress.addIterator(mCakeHouseMenu.getIterator());
    		mWaitress.addIterator(mDinerMenu.getIterator());
    		mWaitress.printMenu();
    	}
    }

# [上述代码 GitHub 地址：https://github.com/baicun/designPatterns][GitHub _https_github.com_baicun_designPatterns] #

[Link 1]: https://blog.csdn.net/csdn_0911/article/details/107810138#%E4%BB%A3%E7%90%86%E6%A8%A1%E5%BC%8F%EF%BC%9A-toc-toc-toc-toc-toc-toc-toc
[Link 2]: https://blog.csdn.net/csdn_0911/article/details/107810138#%E6%A8%A1%E6%9D%BF%E4%BC%98%E7%82%B9%EF%BC%9A
[Link 3]: https://blog.csdn.net/csdn_0911/article/details/107810138#%E6%A8%A1%E6%9D%BF%E6%A8%A1%E5%BC%8F%E5%BA%94%E7%94%A8%EF%BC%9A
[Link 4]: https://blog.csdn.net/csdn_0911/article/details/107810138#%E6%A8%A1%E6%9D%BF%E5%AE%9E%E4%BE%8B%EF%BC%9A
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NzZG5fMDkxMQ_size_16_color_FFFFFF_t_70]: /images/20230208/46fcb04caa89493eb2115843cce86578.png
[GitHub _https_github.com_baicun_designPatterns]: https://blog.csdn.net/csdn_0911/article/details/107810138#%E4%B8%8A%E8%BF%B0%E4%BB%A3%E7%A0%81%20GitHub%20%E5%9C%B0%E5%9D%80%EF%BC%9Ahttps%3A%2F%2Fgithub.com%2Fbaicun%2FdesignPatterns