JAVA设计模式学习笔记-迭代器模式

两个菜馆合并后的菜单问题

蛋糕店与餐厅合并后，怎么统一管理菜单项目
问题：一个用ArrayList管理菜单，一个用数组管理

传统设计

菜单项

package com.java.jikexueyuan.iteratormode;

public class MenuItem {
	private String name,description;
	private boolean vegetable;
	private float price;
	public MenuItem(String name,String description,boolean vegetable,float price)
	{
		this.name=name;
		this.description=description;
		this.vegetable=vegetable;
		this.price=price;
		
	}
	public String getName()
	{
		return name;
	}
	public String getDescription()
	{
		return description;
	}
	public float getPrice()
	{
		return price;
	}
	public boolean  isVegetable()
	{
		return vegetable;
	}
}

蛋糕店菜单

package com.java.jikexueyuan.iteratormode;

import java.util.ArrayList;

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 ArrayList<MenuItem> getMenuItems() {
		return menuItems;
	}
	
	//其他功能代码
}

餐馆菜单

package com.java.jikexueyuan.iteratormode;

import java.util.ArrayList;

public class DinerMenu {
	private final static int Max_Items=5;
	public 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 MenuItem[] getMenuItems() {
		return menuItems;
	}
}

女招待

package com.java.jikexueyuan.iteratormode;

import java.util.ArrayList;

public class Waitress {
	private CakeHouseMenu mCakeHouseMenu;
	private DinerMenu mDinerMenu;
	private ArrayList<MenuItem> cakeitems;
	private MenuItem[] dineritems;

	
	
	public Waitress() {
		mCakeHouseMenu = new CakeHouseMenu();
		cakeitems = mCakeHouseMenu.getMenuItems();

		mDinerMenu = new DinerMenu();
		dineritems = mDinerMenu.getMenuItems();
	}

	public void printMenu() {
		MenuItem menuItem;
		for (int i = 0, len = cakeitems.size(); i < len; i++) {
			menuItem = cakeitems.get(i);
			System.out.println(menuItem.getName() + "***"
					+menuItem.getPrice()+"***"+ menuItem.getDescription());

		}
		for (int i = 0, len = mDinerMenu.numberOfItems; i < len; i++) {
			menuItem = dineritems[i];
			System.out.println(menuItem.getName() + "***"
					+menuItem.getPrice()+"***"+ menuItem.getDescription());

		}

	}

	public void printBreakfastMenu() {

	}

	public void printLunchMenu() {

	}

	public void printVegetableMenu() {

	}
}

迭代器模式

封装遍历，迭代器接口
用迭代器接口改造菜单
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

迭代器接口

package com.java.jikexueyuan.iteratormode.iterator;

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

}

实现迭代器接口

package com.java.jikexueyuan.iteratormode.iterator;

import java.util.ArrayList;

import com.java.jikexueyuan.iteratormode.MenuItem;

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;
		}
	};
}

package com.java.jikexueyuan.iteratormode.iterator;

import java.util.ArrayList;

import com.java.jikexueyuan.iteratormode.MenuItem;

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
	
}

新的女招待

package com.java.jikexueyuan.iteratormode.iterator;

import java.util.ArrayList;

import com.java.jikexueyuan.iteratormode.MenuItem;

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());

			}
			
			
		}
		
		

	}

	public void printBreakfastMenu() {

	}

	public void printLunchMenu() {

	}

	public void printVegetableMenu() {

	}
}

测试类

package com.java.jikexueyuan.iteratormode.iterator;


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();
	}
}