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();
}
}
