设计模式 - 组合模式(composite pattern) 详解

组合模式(composite pattern) 详解

本文地址: http://blog.csdn.net/caroline_wendy

组合模式: 允许你将对象组合成树形结构来表现"整体/部分"层次结构. 组合能让客户以一致的方法处理个别对象以及组合对象.

建立组件类(Component), 组合类(composite)和叶子类(leaf)继承组件类, 客户类(client)直接调用最顶层的组合类(composite)即可.

具体方法:

1. 组件类(component), 包含组合类(composite)和叶子类(leaf)所使用的方法, 即树形结构的一个结点, 使用抽象类(abstract).

如果未定义而使用, 则会抛出异常(exception).

/** * @time 2014年7月4日 */package composite;/** * @author C.L.Wang * */public abstract class MenuComponent {public void add(MenuComponent menuComponent) {throw new UnsupportedOperationException(); //如果未提供, 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();}}

2. 叶子类(leaf)继承组件类(component), 实现特定的输出方法.

/** * @time 2014年7月4日 */package composite;/** * @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 stubthis.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());}}

3. 组合类(composite)继承组件类, 实现所需的方法, 可以添加某些叶子类(leaf)作为子节点.

/** * @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 stubthis.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();}}}

4. 客户类(client)直接调用, 最顶层的组合类(composite)即可.

/** * @time 2014年7月4日 */package composite;/** * @author C.L.Wang * */public class Waitress {MenuComponent allMenus;/** *  */public Waitress(MenuComponent allMenus) {// TODO Auto-generated constructor stubthis.allMenus = allMenus;}public void printMenu() {allMenus.print();}}

5. 测试:

/** * @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 stubMenuComponent 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.printMenu();}}

6. 输出:

ALL MENUS, All menus combined--------------------PANCAKE HOUSE MENU, Breakfast-------------------- K&B's Pancake Breakfast(v), 2.99    -- Pancakes with scrambled eggs, and toast Regular Pancake Breakfast, 2.99    -- Pancakes with fried eggs, sausage Blueberry Pancakes(v), 3.49    -- Pancakes made with fresh blueberries, and blueberry syrup Waffles(v), 3.59    -- Waffles, with your choice of blueberries or strawberriesDINER MENU, Lunch-------------------- Vegetarian BLT(v), 2.99    -- (Fakin') Bacon with lettuce & tomato on whole wheat BLT, 2.99    -- Bacon with lettuce & tomato on whole wheat Soup of the day, 3.29    -- A bowl of the soup of the day, with a side of potato salad Hotdog, 3.05    -- A hot dog, with saurkraut, relish, onions, topped with cheese 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 breadDESSERT MENU, Dessert course!-------------------- 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 limeCAFE MENU, Dinner-------------------- Veggie Burger and Air Fries(v), 3.99    -- Veggie burger on a whole wheat bun, lettuce, tomato, and fries Soup of the day, 3.69    -- A cup of the soup of the day, with a side salad Burrito(v), 4.29    -- A large burrito, with whole pinto beans, salsa, guacamoleCOFFEE MENU, Stuff to go with your afternoon coffee-------------------- Coffee Cake(v), 1.59    -- Crumbly cake topped with cinnamon and walnuts Bagel, 0.69    -- Flavors include sesame, poppyseed, cinnamon raisin, pumpkin Biscotti(v), 0.89    -- Three almond or hazelnut biscotti cookies