设计模式第九集——组合模式（Composite Pattern）

组合模式：利用组合模式可以将对象组合成树形结构来表现“整体/部分”层次结构。组合能让用户以一致的方式处理个别对象以及对象组合。

比如图形界面，Frame或Panel是顶层组件包含其它组件（例如菜单、蚊子面板、滚动条、按钮）这样这个GUI包含了若干部分，当显示的时候认为是一个整体，告诉顶层组件显示，由顶层组件显示左右相关部分。这个包含其它组件的组件为组合对象，成没有包含其它组件的组件为叶节点。

例如，餐厅有多种餐单（咖啡厅餐单、甜点餐单等等）餐单还有子餐单成树形结构。

 代码：

MenuComponent

package com;

public abstract class MenuComponent {
    //组合的方法
    public void add(MenuComponent menuComponent){
        throw new UnsupportedOperationException();
    }
    public void remove(MenuComponent menuComponent){
        throw new UnsupportedOperationException();
    }
    public MenuComponent getChile(int i){
        throw new UnsupportedOperationException();
    }
    //操作方法
    public String getName(){
        throw new UnsupportedOperationException();
    }
    public String getDescription(){
        throw new UnsupportedOperationException();
    }
    public double getPrice(){
        throw new UnsupportedOperationException();
    }
    public void print(){
        throw new UnsupportedOperationException();
    }
}

MenuItem

package com;

public class MenuItem extends MenuComponent {
    String name;
    String description;
    double price;
    
    public MenuItem(String name, String description, double price) {
        
        this.name = name;
        this.description = description;
        this.price = price;
    }

    public String getName() {
        return name;
    }
    
    public String getDescription() {
        return description;
    }
    
    public double getPrice() {
        return price;
    }
    public void print(){
        System.out.println(" "+getName());
        System.out.println(", "+getPrice());
        System.out.println(" -- "+getDescription());
    }
    
    
    
}

Menu:

package com;

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

public class Menu extends MenuComponent {
    ArrayList menuComponents = new ArrayList();
    String name;
    String description;

    public Menu(String name, String description) {
        this.name = name;
        this.description = description;
    }

    @Override
    public void add(MenuComponent menuComponent) {
        // TODO Auto-generated method stub
        menuComponents.add(menuComponent);
    }

    @Override
    public void remove(MenuComponent menuComponent) {
        // TODO Auto-generated method stub
        menuComponents.remove(menuComponent);
    }

    public MenuComponent getChile(int i) {
        // TODO Auto-generated method stub
        return (MenuComponent) menuComponents.get(i);
    }

    @Override
    public String getName() {
        // TODO Auto-generated method stub
        return name;
    }

    @Override
    public String getDescription() {
        // TODO Auto-generated method stub
        return description;
    }

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

        // 用迭代器 遍历所有餐单组件 若果在遍历中遇到了其他餐单或者遇到菜单项
        // 调用print()
        Iterator iterator = menuComponents.iterator();
        while (iterator.hasNext()) {
            MenuComponent menuComponent = (MenuComponent) iterator.next();
            menuComponent.print();
        }
    }

}

Waiteress

package com;

public class Waitress {
    MenuComponent allMenus;

    public Waitress(MenuComponent allMenus) {
        this.allMenus = allMenus;
    }
    
    public void printMenu(){
        allMenus.print();
    }

}

Test:

package com;

public class test {
    public static void main(String args[]){
        MenuComponent pancakeHouseMenu=new Menu("Pancake House Menu","Breakfast");
        MenuComponent dinerMenu=new Menu("Diner Menu","Lunch");
        MenuComponent CaffeeMenu=new Menu("Caffee Menu","Caffee");
        MenuComponent desertMenu=new Menu("Desert Menu","Desert");
        //加入餐单
        MenuComponent allMenus=new Menu("All Menus","All Menus combined");
        allMenus.add(pancakeHouseMenu);
        allMenus.add(dinerMenu);
        allMenus.add(CaffeeMenu);
        allMenus.add(desertMenu);
        
        //加入餐单中的具体内容
        dinerMenu.add(new MenuItem("Pasta","Apaghetti with Marinara",3.89));
        //在dinerMenu中加入另一个餐单desertMenu
        dinerMenu.add(desertMenu);
        desertMenu.add(new MenuItem("Apple Pie","Apple Pie",1.12));
        
        Waitress waitress =new Waitress(allMenus);
        waitress.printMenu();
    }

}