Java设计模式 - 迭代器模式

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：

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：

耦合度低，灵活

迭代器模式应用：

Java内置迭代器

迭代器实例：

类图：

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