Composite Pattern

public abstract class MenuComponent {
	// 메소드들은 하위 클래스에서 구현하지 않을 경우 기본적으로 오류 던지도록 구현
   
    // MenuComponent 관련 메소드
	public void add(MenuComponent menuComponent) {
		throw new UnsupportedOperationException();
	}
	public void remove(MenuComponent menuComponent) {
		throw new UnsupportedOperationException();
	}
	public MenuComponent getChild(int i) {
		throw new UnsupportedOperationException();
	}
  
    // MenuItem 관련 메소드
	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 class MenuItem extends MenuComponent {
	String name;
	String description;
	boolean vegetarian;
	double price;
    
	public MenuItem(String name, 
	                String description, 
	                boolean vegetarian, 
	                double price) 
	{ 
		this.name = name;
		this.description = description;
		this.vegetarian = vegetarian;
		this.price = price;
	}
  
  	// 필요한 메소드 재정의
	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 class Menu extends MenuComponent {
	ArrayList<MenuComponent> menuComponents = new ArrayList<MenuComponent>();
	String name;
	String description;
  
	public Menu(String name, String description) {
		this.name = name;
		this.description = description;
	}
 
 	// 필요한 메소드 재정의
	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("---------------------");
  		
        // 이터레이터 패턴 사용하여 반복
		Iterator<MenuComponent> iterator = menuComponents.iterator();
		while (iterator.hasNext()) {
			MenuComponent menuComponent = 
				(MenuComponent)iterator.next();
			menuComponent.print();
		}
	}
}

public class Waitress {
	MenuComponent allMenus;
 	
    // 다른 모든 메뉴를 포함하고 있는 최상위 메뉴 구성요소 넘겨주기
	public Waitress(MenuComponent allMenus) {
		this.allMenus = allMenus;
	}
 
 	// 최상위 메뉴 구성요소 출력하면 트리에 속한 모든 메뉴 출력 가능
	public void printMenu() {
		allMenus.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
		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
		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(
			"Hot Dog",
			"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));
   
   		// dinerMenu에 dessertMenu 추가
		dinerMenu.add(dessertMenu);
  
  		// 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
		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));

		// cafeMenu에 coffeeMenu 추가
		cafeMenu.add(coffeeMenu);

		// 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();		// print
	}
}

public class Menu extends MenuComponent {
	Iterator<MenuComponent> iterator = null;
    .
    .
    .

	// Menu에 CompositeIterator 추가
    // 현재 복합 객체에 대한 반복자 리턴
	public Iterator<MenuComponent> createIterator() {
		if (iterator == null) {
			iterator = new CompositeIterator(menuComponents.iterator());
		}
		return iterator;
	}
.
.
.

public class MenuItem extends MenuComponent {
 
.
.
.
	// NullItertor 추가
    // Leaf는 반복자가 존재하지 않으므로 아무 일도 하지 않는 null 반복자 리턴
	public Iterator<MenuComponent> createIterator() {
		return new NullIterator();
	}
 .
 .
 .

public class CompositeIterator implements Iterator<MenuComponent> {
	// 위의 코드에서는 leaf node 안에서 반복자를 써서 작업을 처리하고 composite인 경우 하위 메서드를 호출하여 반복
    // 하지만 해당 코드에서는 iterator를 사용하므로 외부에서 반복자 사용 -> 스택 사용해야 함
	Stack<Iterator<MenuComponent>> stack = new Stack<Iterator<MenuComponent>>();
   
   // 최상위 composite의 iterator 전달
	public CompositeIterator(Iterator<MenuComponent> iterator) {
		stack.push(iterator);
	}
   
	public MenuComponent next() {
		if (hasNext()) {
			Iterator<MenuComponent> iterator = stack.peek();
			MenuComponent component = iterator.next();
			stack.push(component.createIterator());
			return component;
		} else {
			return null;
		}
	}
  
	public boolean hasNext() {
		if (stack.empty()) {
			return false;
		} else {
			Iterator<MenuComponent> iterator = stack.peek();
			if (!iterator.hasNext()) {
				stack.pop();
				return hasNext();
			} else {
				return true;
			}
		}
	}
	
	/*
	 * No longer needed as of Java 8
	 * 
	 * (non-Javadoc)
	 * @see java.util.Iterator#remove()
	 *
	public void remove() {
		throw new UnsupportedOperationException();
	}
	*/
}

public class Waitress {
	MenuComponent allMenus;
 
	public Waitress(MenuComponent allMenus) {
		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()) {	
        	// iterator 이용해서 채식주의자 메뉴만 출력
			MenuComponent menuComponent = iterator.next();
			try {
				if (menuComponent.isVegetarian()) {
					menuComponent.print();
				}
			} catch (UnsupportedOperationException e) {}
            // 여기서 try-catch를 사용한 이유
            // client에서 composite, leaf를 똑같이 취급하고 composite에서 지원하지 않는 메소드임을 나타내기 위해서 사용
		}
	}
}