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

 1 package com;
 2 
 3 public abstract class MenuComponent {
 4     //组合的方法
 5     public void add(MenuComponent menuComponent){
 6         throw new UnsupportedOperationException();
 7     }
 8     public void remove(MenuComponent menuComponent){
 9         throw new UnsupportedOperationException();
10     }
11     public MenuComponent getChile(int i){
12         throw new UnsupportedOperationException();
13     }
14     //操作方法
15     public String getName(){
16         throw new UnsupportedOperationException();
17     }
18     public String getDescription(){
19         throw new UnsupportedOperationException();
20     }
21     public double getPrice(){
22         throw new UnsupportedOperationException();
23     }
24     public void print(){
25         throw new UnsupportedOperationException();
26     }
27 }

MenuItem

 1 package com;
 2 
 3 public class MenuItem extends MenuComponent {
 4     String name;
 5     String description;
 6     double price;
 7     
 8     public MenuItem(String name, String description, double price) {
 9         
10         this.name = name;
11         this.description = description;
12         this.price = price;
13     }
14 
15     public String getName() {
16         return name;
17     }
18     
19     public String getDescription() {
20         return description;
21     }
22     
23     public double getPrice() {
24         return price;
25     }
26     public void print(){
27         System.out.println(" "+getName());
28         System.out.println(", "+getPrice());
29         System.out.println(" -- "+getDescription());
30     }
31     
32     
33     
34 }

Menu:

 1 package com;
 2 
 3 import java.util.ArrayList;
 4 import java.util.Iterator;
 5 
 6 public class Menu extends MenuComponent {
 7     ArrayList menuComponents = new ArrayList();
 8     String name;
 9     String description;
10 
11     public Menu(String name, String description) {
12         this.name = name;
13         this.description = description;
14     }
15 
16     @Override
17     public void add(MenuComponent menuComponent) {
18         // TODO Auto-generated method stub
19         menuComponents.add(menuComponent);
20     }
21 
22     @Override
23     public void remove(MenuComponent menuComponent) {
24         // TODO Auto-generated method stub
25         menuComponents.remove(menuComponent);
26     }
27 
28     public MenuComponent getChile(int i) {
29         // TODO Auto-generated method stub
30         return (MenuComponent) menuComponents.get(i);
31     }
32 
33     @Override
34     public String getName() {
35         // TODO Auto-generated method stub
36         return name;
37     }
38 
39     @Override
40     public String getDescription() {
41         // TODO Auto-generated method stub
42         return description;
43     }
44 
45     @Override
46     public void print() {
47         System.out.println("\n" + getName());
48         System.out.println(", " + getDescription());
49         System.out.println("--------------------");
50 
51         // 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
52         // 调用print()
53         Iterator iterator = menuComponents.iterator();
54         while (iterator.hasNext()) {
55             MenuComponent menuComponent = (MenuComponent) iterator.next();
56             menuComponent.print();
57         }
58     }
59 
60 }

Waiteress

package com;

public class Waitress {
    MenuComponent allMenus;

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

}

Test:

 1 package com;
 2 
 3 public class test {
 4     public static void main(String args[]){
 5         MenuComponent pancakeHouseMenu=new Menu("Pancake House Menu","Breakfast");
 6         MenuComponent dinerMenu=new Menu("Diner Menu","Lunch");
 7         MenuComponent CaffeeMenu=new Menu("Caffee Menu","Caffee");
 8         MenuComponent desertMenu=new Menu("Desert Menu","Desert");
 9         //加入餐单
10         MenuComponent allMenus=new Menu("All Menus","All Menus combined");
11         allMenus.add(pancakeHouseMenu);
12         allMenus.add(dinerMenu);
13         allMenus.add(CaffeeMenu);
14         allMenus.add(desertMenu);
15         
16         //加入餐单中的具体内容
17         dinerMenu.add(new MenuItem("Pasta","Apaghetti with Marinara",3.89));
18         //在dinerMenu中加入另一个餐单desertMenu
19         dinerMenu.add(desertMenu);
20         desertMenu.add(new MenuItem("Apple Pie","Apple Pie",1.12));
21         
22         Waitress waitress =new Waitress(allMenus);
23         waitress.printMenu();
24     }
25 
26 }