设计模式 - 组合模式(composite pattern) 迭代器(iterator) 具体解释

组合模式(composite pattern) 迭代器(iterator) 具体解释

本文地址: http://blog.csdn.net/caroline_wendy
參考组合模式(composite pattern): http://blog.csdn.net/caroline_wendy/article/details/36895627
在组合模式(composite pattern)加入迭代器功能, 遍历每个组合(composite)的项.

具体方法:

1. 抽象组件类(abstract component)加入创建迭代器的方法.

/**
* @time 2014年7月4日
*/
package composite;

import java.util.Iterator;

/**
* @author C.L.Wang
*
*/
public abstract class MenuComponent {
public void add(MenuComponent menuComponent) {
throw new UnsupportedOperationException(); //假设未提供, 则不能调用
}
public void remove(MenuComponent menuComponent) {
throw new UnsupportedOperationException();
}
public MenuComponent getChild(int i) {
throw new UnsupportedOperationException();
}
public String getName() {
throw new UnsupportedOperationException();
}
public String getDescription() {
throw new UnsupportedOperationException();
}
public double getPrice() {
throw new UnsupportedOperationException();
}
public boolean isVegetarian() {
throw new UnsupportedOperationException();
}
public void print() {
throw new UnsupportedOperationException();
}
public Iterator<MenuComponent> createIterator() {
throw new UnsupportedOperationException();
}
}

2. 组合迭代器类(composite iterator).

/**
* @time 2014年7月4日
*/
package composite;

import java.util.Iterator;
import java.util.Stack;

/**
* @author C.L.Wang
*
*/
public class CompositeIterator implements Iterator<MenuComponent> {

Stack<Iterator<MenuComponent>> stack = new Stack<Iterator<MenuComponent>>();

/**
*
*/
public CompositeIterator(Iterator<MenuComponent> iterator) {
// TODO Auto-generated constructor stub
stack.push(iterator);
}

public boolean hasNext() {
if (stack.empty()) {
return false;
} else {
Iterator<MenuComponent> iterator = (Iterator<MenuComponent>)stack.peek();
if (!iterator.hasNext()) {
stack.pop();
return hasNext(); //递归调用
} else {
return true;
}
}
}

public MenuComponent next() {
if (hasNext()) {
Iterator<MenuComponent> iterator = (Iterator<MenuComponent>)stack.peek();
MenuComponent component = (MenuComponent)iterator.next();
if (component instanceof Menu) {
stack.push(component.createIterator());
}
return component;
} else {
return null;
}
}

public void remove() {
throw new UnsupportedOperationException();
}

}

3. 组合类(composite)实现创建迭代器的方法, 并创建组合迭代器(composite iterator).

/**
* @time 2014年7月4日
*/
package composite;

import java.util.ArrayList;
import java.util.Iterator;

/**
* @author C.L.Wang
*
*/
public class Menu extends MenuComponent {

ArrayList<MenuComponent> menuComponents = new ArrayList<MenuComponent>();
String name;
String description;

/**
*
*/
public Menu(String name, String description) {
// TODO Auto-generated constructor stub
this.name = name;
this.description = description;
}

public void add(MenuComponent menuComponent) {
menuComponents.add(menuComponent);
}

public void remove(MenuComponent menuComponent) {
menuComponents.remove(menuComponent);
}

public MenuComponent getChild(int i) {
return (MenuComponent)menuComponents.get(i);
}
public String getName() {
return name;
}

public String getDescription() {
return description;
}

public void print() {
System.out.print("\n" + getName());
System.out.println(", " + getDescription());
System.out.println("--------------------");

Iterator<MenuComponent> iterator = menuComponents.iterator();
while (iterator.hasNext()) {
MenuComponent menuComponent = (MenuComponent)iterator.next();
menuComponent.print();
}
}

public Iterator<MenuComponent> createIterator() {
return new CompositeIterator(menuComponents.iterator());
}

}

4. 叶子类(leaf)实现创建空迭代器(null iterator)的方法.

/**
* @time 2014年7月4日
*/
package composite;

import java.util.Iterator;

/**
* @author C.L.Wang
*
*/
public class NullIterator implements Iterator<MenuComponent> {
public MenuComponent next() {
return null;
}
public boolean hasNext() {
return false;
}
public void remove() {
throw new UnsupportedOperationException();
}
}

/**
* @time 2014年7月4日
*/
package composite;

import java.util.Iterator;

/**
* @author C.L.Wang
*
*/
public class MenuItem extends MenuComponent {

String name;
String description;
boolean vegetarian;
double price;
/**
*
*/
public MenuItem(String name, String description,
boolean vegetarian, double price) {
// TODO Auto-generated constructor stub
this.name = name;
this.description = description;
this.vegetarian = vegetarian;
this.price = price;
}

public String getName() {
return name;
}
public String getDescription() {
return description;
}
public double getPrice() {
return price;
}
public boolean isVegetarian() {
return vegetarian;
}
public void print() {
System.out.print(" " + getName());
if (isVegetarian()) {
System.out.print("(v)");
}
System.out.println(", " + getPrice());
System.out.println("    -- " + getDescription());
}
public Iterator<MenuComponent> createIterator() {
return new NullIterator();
}
}

5. 客户类.

/**
* @time 2014年7月4日
*/
package composite;

import java.util.Iterator;

/**
* @author C.L.Wang
*
*/
public class Waitress {

MenuComponent allMenus;
/**
*
*/
public Waitress(MenuComponent allMenus) {
// TODO Auto-generated constructor stub
this.allMenus = allMenus;
}

public void printMenu() {
allMenus.print();
}

public void printVegetarianMenu() {
Iterator<MenuComponent> iterator = allMenus.createIterator();
System.out.println("\nVEGETARIAN MENU\n----");
while (iterator.hasNext()) {
MenuComponent menuComponent = (MenuComponent)iterator.next();
try {
if (menuComponent.isVegetarian())
menuComponent.print();
} catch (UnsupportedOperationException ex) {}
}
}

}

6. 測试类

/**
* @time 2014年7月4日
*/
package composite;

/**
* @author C.L.Wang
*
*/
public class MenuTestDrive {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
MenuComponent pancakeHouseMenu = new Menu("PANCAKE HOUSE MENU", "Breakfast");
MenuComponent dinerMenu = new Menu("DINER MENU", "Lunch");
MenuComponent cafeMenu = new Menu("CAFE MENU", "Dinner");
MenuComponent dessertMenu = new Menu("DESSERT MENU", "Dessert course!");
MenuComponent coffeeMenu = new Menu("COFFEE MENU", "Stuff to go with your afternoon coffee");

MenuComponent allMenus = new Menu("ALL MENUS", "All menus combined");

allMenus.add(pancakeHouseMenu);
allMenus.add(dinerMenu);
allMenus.add(cafeMenu);

pancakeHouseMenu.add(new MenuItem(
"K&B's Pancake Breakfast",
"Pancakes with scrambled eggs, and toast",
true,
2.99));
pancakeHouseMenu.add(new MenuItem(
"Regular Pancake Breakfast",
"Pancakes with fried eggs, sausage",
false,
2.99));
pancakeHouseMenu.add(new MenuItem(
"Blueberry Pancakes",
"Pancakes made with fresh blueberries, and blueberry syrup",
true,
3.49));
pancakeHouseMenu.add(new MenuItem(
"Waffles",
"Waffles, with your choice of blueberries or strawberries",
true,
3.59));

dinerMenu.add(new MenuItem(
"Vegetarian BLT",
"(Fakin') Bacon with lettuce & tomato on whole wheat",
true,
2.99));
dinerMenu.add(new MenuItem(
"BLT",
"Bacon with lettuce & tomato on whole wheat",
false,
2.99));
dinerMenu.add(new MenuItem(
"Soup of the day",
"A bowl of the soup of the day, with a side of potato salad",
false,
3.29));
dinerMenu.add(new MenuItem(
"Hotdog",
"A hot dog, with saurkraut, relish, onions, topped with cheese",
false,
3.05));
dinerMenu.add(new MenuItem(
"Steamed Veggies and Brown Rice",
"Steamed vegetables over brown rice",
true,
3.99));

dinerMenu.add(new MenuItem(
"Pasta",
"Spaghetti with Marinara Sauce, and a slice of sourdough bread",
true,
3.89));

dinerMenu.add(dessertMenu);

dessertMenu.add(new MenuItem(
"Apple Pie",
"Apple pie with a flakey crust, topped with vanilla icecream",
true,
1.59));

dessertMenu.add(new MenuItem(
"Cheesecake",
"Creamy New York cheesecake, with a chocolate graham crust",
true,
1.99));
dessertMenu.add(new MenuItem(
"Sorbet",
"A scoop of raspberry and a scoop of lime",
true,
1.89));

cafeMenu.add(new MenuItem(
"Veggie Burger and Air Fries",
"Veggie burger on a whole wheat bun, lettuce, tomato, and fries",
true,
3.99));
cafeMenu.add(new MenuItem(
"Soup of the day",
"A cup of the soup of the day, with a side salad",
false,
3.69));
cafeMenu.add(new MenuItem(
"Burrito",
"A large burrito, with whole pinto beans, salsa, guacamole",
true,
4.29));

cafeMenu.add(coffeeMenu);

coffeeMenu.add(new MenuItem(
"Coffee Cake",
"Crumbly cake topped with cinnamon and walnuts",
true,
1.59));
coffeeMenu.add(new MenuItem(
"Bagel",
"Flavors include sesame, poppyseed, cinnamon raisin, pumpkin",
false,
0.69));
coffeeMenu.add(new MenuItem(
"Biscotti",
"Three almond or hazelnut biscotti cookies",
true,
0.89));

Waitress waitress = new Waitress(allMenus);

waitress.printVegetarianMenu();
}

}

7. 输出.

VEGETARIAN MENU
----
K&B's Pancake Breakfast(v), 2.99
-- Pancakes with scrambled eggs, and toast
Blueberry Pancakes(v), 3.49
-- Pancakes made with fresh blueberries, and blueberry syrup
Waffles(v), 3.59
-- Waffles, with your choice of blueberries or strawberries
Vegetarian BLT(v), 2.99
-- (Fakin') Bacon with lettuce & tomato on whole wheat
Steamed Veggies and Brown Rice(v), 3.99
-- Steamed vegetables over brown rice
Pasta(v), 3.89
-- Spaghetti with Marinara Sauce, and a slice of sourdough bread
Apple Pie(v), 1.59
-- Apple pie with a flakey crust, topped with vanilla icecream
Cheesecake(v), 1.99
-- Creamy New York cheesecake, with a chocolate graham crust
Sorbet(v), 1.89
-- A scoop of raspberry and a scoop of lime
Apple Pie(v), 1.59
-- Apple pie with a flakey crust, topped with vanilla icecream
Cheesecake(v), 1.99
-- Creamy New York cheesecake, with a chocolate graham crust
Sorbet(v), 1.89
-- A scoop of raspberry and a scoop of lime
Veggie Burger and Air Fries(v), 3.99
-- Veggie burger on a whole wheat bun, lettuce, tomato, and fries
Burrito(v), 4.29
-- A large burrito, with whole pinto beans, salsa, guacamole
Coffee Cake(v), 1.59
-- Crumbly cake topped with cinnamon and walnuts
Biscotti(v), 0.89
-- Three almond or hazelnut biscotti cookies
Coffee Cake(v), 1.59
-- Crumbly cake topped with cinnamon and walnuts
Biscotti(v), 0.89
-- Three almond or hazelnut biscotti cookies