DP-详解组合模式代码实现

组合模式（composite pattern）：将对象组合成树形结构来表现部分-整体层次结构。组合让客户可以统一处理个别对象和对象组合。

java 复制代码

package com.designpatterns.composite;

/**
 * 1.实现MenuComponent
 */
public abstract class MenuComponent {
    public void add(MenuComponent menuComponent){
        throw new UnsupportedOperationException();
    }
    public void remove(MenuComponent menuComponent){
        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();
    }
}

java 复制代码

package com.designpatterns.composite;

import java.util.ArrayList;
import java.util.List;

/**
 * 2.实现菜单
 */
public class Menu extends  MenuComponent{
    List<MenuComponent> 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) {
        menuComponents.add(menuComponent);
    }

    @Override
    public void remove(MenuComponent menuComponent) {
        menuComponents.remove(menuComponent);
    }

    public MenuComponent getChild(int i){
        return menuComponents.get(i);
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public String getDescription() {
        return description;
    }

    @Override
    public void print() {
        System.out.println("\n" + getName());
        System.out.println(", "+getDescription());
        System.out.println("---------------------------");
        for (MenuComponent menuComponent : menuComponents) {
            menuComponent.print();
        }
    }
}

java 复制代码

package com.designpatterns.composite;

/**
 * 3.实现MenuItem
 */
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;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public String getDescription() {
        return description;
    }

    @Override
    public double getPrice() {
        return price;
    }

    @Override
    public boolean isVegetarian() {
        return vegetarian;
    }

    @Override
    public void print() {
        System.out.println(" "+getName());
        if(isVegetarian()){
            System.out.println("(v)");
        }
        System.out.println(", "+getPrice());
        System.out.println("  --"+getDescription());
    }
}

java 复制代码

package com.designpatterns.composite;

/**
 * 4.定义服务员
 */
public class Waitress {
    MenuComponent allMenus;
    public Waitress(MenuComponent allMenus){
        this.allMenus=allMenus;
    }

    public void printMenu(){
        allMenus.print();
    }
}

java 复制代码

package com.designpatterns.composite;

/**
 * 5.测试组合模式
 */
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 allMenus=new Menu("ALL Menus","ALL menus combined");

        allMenus.add(pancakeHouseMenu);
        allMenus.add(dinerMenu);
        allMenus.add(cafeMenu);

        //添加菜单项
        dinerMenu.add(new MenuItem(
                "Pasta",
                "Bread",
                true,
                3.89
        ));
        dinerMenu.add(dessertMenu);

        dessertMenu.add(new MenuItem(
                "Apple Pie",
                "ice cream",
                true,
                1.59
        ));

        //添加所有菜单
        Waitress waitress=new Waitress(allMenus);
        waitress.printMenu();

    }
}

最终测试结果如下：