Java设计模式(十一)：组合设计模式

忘是亡心i 2022-03-30 14:54 206阅读 0赞

# 1. 应用场景 #

这种组合模式正是应树形结构而生，所以组合模式的使用场景就是出现树形结构的地方。比如：文件目录显示，多及目录呈现等树形结构数据的操作。

# 2. 概念 #

将对象组合成树形结构来表示“整体/部分”层次关系，允许用户以相同的方式处理单独对象和组合对象。

# 3. Class Diagram #

组件（Component）类是组合类（Composite）和叶子类（Leaf）的父类，可以把组合类看成是树的中间节点。

组合对象拥有一个或者多个组件对象，因此组合对象的操作可以委托给组件对象去处理，而组件对象可以是另一个组合对象或者叶子对象。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxMTI1MTgz_size_16_color_FFFFFF_t_70]

# 4. Implementation #

public abstract class MenuComponent { 
        public void add(MenuComponent menuComponent){ 
            throw new UnsupportedOperationException();
        }
    
        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 createIterator(){ 
            throw new UnsupportedOperationException();
        }
    }
    
    public class Menu extends MenuComponent { 
        private ArrayList<MenuComponent> menuComponents=new ArrayList<>();
        private String name;
        private String description;
    
        public Menu(String name, String description) { 
            this.name = name;
            this.description = description;
        }
    
        @Override
        public void add(MenuComponent menuComponent) { 
            menuComponents.add(menuComponent);
        }
    
        @Override
        public void remove(MenuComponent menuComponent) { 
            menuComponents.remove(menuComponent);
        }
    
        @Override
        public MenuComponent getChild(int i) { 
            return menuComponents.get(i);
        }
    
        @Override
        public String getName() { 
            return name;
        }
    
        @Override
        public String getDescription() { 
            return description;
        }
    
        @Override
        public double getPrice() { 
            return super.getPrice();
        }
    
        @Override
        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 = iterator.next();
                menuComponent.print();
            }
        }
    }
    
    public class MenuItem extends MenuComponent { 
        private String name;
        private String decription;
        private boolean vegetarian;
        private double price;
    
        public MenuItem(String name, String decription, boolean vegetarian, double price) { 
            this.name = name;
            this.decription = decription;
            this.vegetarian = vegetarian;
            this.price = price;
        }
    
        @Override
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        @Override
        public String getDescription() { 
            return decription;
        }
    
        @Override
        public boolean isVegetarian() { 
            return vegetarian;
        }
    
        public void setVegetarian(boolean vegetarian) { 
            this.vegetarian = vegetarian;
        }
    
        @Override
        public double getPrice() { 
            return price;
        }
    
        public void setPrice(double price) { 
            this.price = price;
        }
    
        public void print() { 
            System.out.print(" " + getName());
            if (isVegetarian()) { 
                System.out.print("(v)");
            }
            System.out.println(", " + getPrice());
            System.out.println(" -- " + getDescription());
        }
    }
    
    public class Waitress { 
        private MenuComponent menuComponent;
    
        public Waitress(MenuComponent menuComponent) { 
            this.menuComponent = menuComponent;
        }
    
        public void printMenu(){ 
            menuComponent.print();
        }
    }
    
    public class MenuTestDrive { 
    	public static void main(String args[]) { 
    		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 of 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();
    	}
    }

# 5. JDK #

*  javax.swing.JComponent\#add(Component)
 *  java.awt.Container\#add(Component)
 *  java.util.Map\#putAll(Map)
 *  java.util.List\#addAll(Collection)
 *  java.util.Set\#addAll(Collection)

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