Java设计模式 - 组合模式

目录

组合模式：

组合优点：

组合模式应用：

组合实例：

上述代码 GitHub 地址：https://github.com/baicun/designPatterns

组合模式：

处理具有树形结构的设计模式，具体使用一致的方式来处理个别对象以及不同对象组合。

组合优点：

兼容性强，不必关心处理的是单个对象还是整个组合结构

组合模式应用：

java.AWT Component中的组合模式

组合实例：

类图：

示例：俩家不同的餐馆合并，需要打印出不同组合的菜单，面包馆呢是遍历的集合，而小饭馆呢是遍历的数组，所以需要找一个统一的方法，来解决这个问题，之前使用的迭代器模式进行设计，现在想在小饭馆菜单中增加饭后甜点，他和小饭馆菜是菜单包含菜单，我们称之为容器，这个时候，就需要使用组合模式。

代码：

创建一个大的容器类-MenuComponent.java

public abstract class MenuComponent {

	public String getName() {
		return "";
	}

	public String getDescription() {
		return "";
	}

	public float getPrice() {
		return 0;
	}

	public boolean isVegetable() {
		return false;
	}

	public abstract void print();

	public Iterator getIterator() {
		return new NullIterator();
	}
}

面包馆菜单-CakeHouseMenu.java

public class CakeHouseMenu extends MenuComponent {
    private ArrayList<MenuComponent> menuItems;

    public CakeHouseMenu() {
        menuItems = new ArrayList<MenuComponent>();

        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 ComposeIterator(menuItems.iterator());
    }

    @Override
    public void print() {
        System.out.println("****This is CakeHouseMenu****");
    }
}

 小饭馆菜单-DinerMenu.java

public class DinerMenu extends MenuComponent {
    private final static int Max_Items = 5;
    private int numberOfItems = 0;
    private MenuComponent[] menuItems;

    public DinerMenu() {
        menuItems = new MenuComponent[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);
        // 新增饭后甜点
        addSubMenu(new SubMenu());

    }

    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++;
        }

    }
    private void addSubMenu(MenuComponent mMenuComponent) {
        if (numberOfItems >= Max_Items) {
            System.err.println("sorry,menu is full!can not add another item");
        } else {
            menuItems[numberOfItems] = mMenuComponent;
            numberOfItems++;
        }

    }

    public Iterator getIterator() {
        return new ComposeIterator(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
            MenuComponent menuItem = menuItems[position];
            position++;
            return menuItem;
        }

        @Override
        public void remove() {
            // TODO Auto-generated method stub
        }
    }

    @Override
    public void print() {
        System.out.println("****This is DinerMenu****");
    }
}

饭后甜点-SubMenu.java,集成超类，方便遍历子元素。

public class SubMenu extends MenuComponent {
	private ArrayList<MenuComponent> menuItems;

	public SubMenu() {
		menuItems = new ArrayList<MenuComponent>();

		addItem("Apple Cookie", "Apple&candy&Cookie", true, 1.99f);
		addItem("Banana Cookie", "Banana&candy&Cookie", false, 1.59f);
		addItem("Orange Cookie", "Orange&Cookie", true, 1.29f);
	}

	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 ComposeIterator(menuItems.iterator());
	}

	@Override
	public void print() {
		System.out.println("****This is SubMenu****");
	};
	// 其他功能代码

}

测试类：

public class MainTest {
	public static void main(String[] args) {
		Waitress mWaitress = new Waitress();
		CakeHouseMenu mCakeHouseMenu = new CakeHouseMenu();
		DinerMenu mDinerMenu = new DinerMenu();
		mWaitress.addComponent(mCakeHouseMenu);
		mWaitress.addComponent(mDinerMenu);
		mWaitress.printVegetableMenu();;
	}
}

上述代码 GitHub 地址：https://github.com/baicun/designPatterns