23种设计模式自我探索之建造者模式

23种设计模式自我探索

建造者模式

建造者模式，使用多个简单的对象一步一步构建成一个复杂的对象 本次探索示例模拟美团、肯德基下单点餐打印订单信息

众所周知，咱们到麦当劳和肯德基点餐，最终目的是为了获取到对应食物 本例中食物Meal作为最终输出对象 食物包含名字，包装，金额等信息，不同种类的食物（蔬菜和肉类）继承食物种类（吃的和喝的），而吃的和喝的实现总接口Item 通过继承和实现，最终每个食物都属于Item，输出Item列表，即展示了食物列表 闲话少说，直接上代码

package com.ttjb.demo.model.builder; public interface Item { public String name(); public Packing packing(); public float price(); } package com.ttjb.demo.model.builder; public interface Packing { public String pack(); }

吃的和喝的进行包装时，分别可以通过包装盒和瓶子（杯子也行）进行包装，这时候只需要通过两个Packing的实现类进行包装方式的区分即可

package com.ttjb.demo.model.builder.packing; import com.ttjb.demo.model.builder.Packing; public class Bottle implements Packing { @Override public String pack() { return "Bottle"; } } package com.ttjb.demo.model.builder.packing; import com.ttjb.demo.model.builder.Packing; public class Wrapper implements Packing { @Override public String pack() { return "Wrapper"; } }

吃的和喝的都属于Item，作为商品都应该具有name，packing和price等属性，所以需要实现Item接口

package com.ttjb.demo.model.builder.goods.type; import com.ttjb.demo.model.builder.Item; import com.ttjb.demo.model.builder.Packing; import com.ttjb.demo.model.builder.packing.Wrapper; public abstract class Burger implements Item { @Override public Packing packing() { return new Wrapper(); } @Override public abstract float price(); } package com.ttjb.demo.model.builder.goods.type; import com.ttjb.demo.model.builder.packing.Bottle; import com.ttjb.demo.model.builder.Item; import com.ttjb.demo.model.builder.Packing; public abstract class ColdDrink implements Item { @Override public Packing packing() { return new Bottle(); } @Override public abstract float price(); }

而吃的和喝的可以细分具体的食物和饮料，这里以炸鸡🐔、汉堡🍔、橙汁🍊和可乐作为示例

package com.ttjb.demo.model.builder.goods; import com.ttjb.demo.model.builder.goods.type.Burger; public class FriedChicken extends Burger { @Override public String name() { return "Fried Chicken"; } @Override public float price() { return 30.0f; } } package com.ttjb.demo.model.builder.goods; import com.ttjb.demo.model.builder.goods.type.Burger; public class Hamburger extends Burger { @Override public String name() { return "Hamburger"; } @Override public float price() { return 15.0f; } } package com.ttjb.demo.model.builder.goods; import com.ttjb.demo.model.builder.goods.type.ColdDrink; public class Orange extends ColdDrink { @Override public String name() { return "Orange"; } @Override public float price() { return 3.0f; } } package com.ttjb.demo.model.builder.goods; import com.ttjb.demo.model.builder.goods.type.ColdDrink; public class Coke extends ColdDrink { @Override public String name() { return "Coke"; } @Override public float price() { return 20.0f; } }

准备工作做完之后，开始构造最终输出对象Meal，需要包含价格和相关食物条目信息

package com.ttjb.demo.model.builder.meals; import com.ttjb.demo.model.builder.Item; import java.util.ArrayList; import java.util.List; public class Meal { private List<Item> itemList = new ArrayList<>(); public void addItem(Item item) { itemList.add(item); } public float getCost() { float cost = 0.0f; for (Item item : itemList) { cost += item.price(); } return cost; } public void showItems() { for (Item item : itemList) { System.out.print("Item : " + item.name()); System.out.print(", Packing : " + item.packing().pack()); System.out.println(", Price : " + item.price()); } } }

开始造食物

package com.ttjb.demo.model.builder.meals; import com.ttjb.demo.model.builder.Item; public class MealBuilderWithParam { public Meal prepareVegMeal(Item... item) { Meal meal = new Meal(); for (int i = 0; i < item.length; i++) { meal.addItem(item[i]); } return meal; } public Meal prepareNonVegMeal(Item... item) { Meal meal = new Meal(); for (int i = 0; i < item.length; i++) { meal.addItem(item[i]); } return meal; } }

测试代码，打印订单信息

package com.ttjb.demo.model.builder; import com.ttjb.demo.model.builder.goods.*; import com.ttjb.demo.model.builder.meals.Meal; import com.ttjb.demo.model.builder.meals.MealBuilder; import com.ttjb.demo.model.builder.meals.MealBuilderWithParam; /** * 建造者模式 * 使用多个简单的对象一步一步构建成一个复杂的对象 * 食物Meal作为最终输出对象 * 食物包含名字，包装，金额，不同种类的食物（蔬菜和肉类）继承食物种类（吃的和喝的），而吃的和喝的实现总接口Item * 通过继承和实现，最终每个食物都属于Item，输出Item列表，即展示了食物列表 */ public class TestBuilderModelWithParam { public static void main(String[] args) { MealBuilderWithParam mealBuilder = new MealBuilderWithParam(); System.out.println("========================================="); Meal vegMeal = mealBuilder.prepareVegMeal(new Orange(), new Hamburger(), new Coke()); System.out.println("Veg Meal"); vegMeal.showItems(); System.out.println("Total Cost: " + vegMeal.getCost()); System.out.println("========================================="); Meal nonVegMeal = mealBuilder.prepareNonVegMeal(new FriedChicken(), new Coke()); System.out.println("Non-Veg Meal"); nonVegMeal.showItems(); System.out.println("Total Cost: " + nonVegMeal.getCost()); System.out.println("========================================="); Meal drink = mealBuilder.prepareNonVegMeal(new Coke()); System.out.println("Drink Meal"); drink.showItems(); System.out.println("Total Cost: " + drink.getCost()); } }

输出结果

========================================= Veg Meal Item : Orange, Packing : Bottle, Price : 3.0 Item : Hamburger, Packing : Wrapper, Price : 15.0 Item : Coke, Packing : Bottle, Price : 20.0 Total Cost: 38.0 ========================================= Non-Veg Meal Item : Fried Chicken, Packing : Wrapper, Price : 30.0 Item : Coke, Packing : Bottle, Price : 20.0 Total Cost: 50.0 ========================================= Drink Meal Item : Coke, Packing : Bottle, Price : 20.0 Total Cost: 20.0

参考文献：https://www.runoob.com/design-pattern/builder-pattern.html 虽然说也是从其他博客上学习的，但是加入了自己的理解，仅以此文铭记，供大大们参考