参考:http://www.runoob.com/design-pattern/builder-pattern.html
源码下载:https://github.com/gpqhl0071/pattern.git
建造者模式(Builder Pattern)使用多个简单的对象一步一步构建成一个复杂的对象。这种类型的设计模式属于创建型模式,它提供了一种创建对象的最佳方式。
事例
我们假设一个快餐店的商业案例,其中,一个典型的套餐可以是一个汉堡(Burger)和一杯冷饮(Cold drink)。汉堡(Burger)可以是素食汉堡(Veg Burger)或鸡肉汉堡(Chicken Burger),它们是包在纸盒中。冷饮(Cold drink)可以是可口可乐(coke)或百事可乐(pepsi),它们是装在瓶子中。
我们将创建一个表示食物条目(比如汉堡和冷饮)的 Item 接口和实现 Item 接口的实体类,以及一个表示食物包装的 Packing 接口和实现 Packing 接口的实体类,汉堡是包在纸盒中,冷饮是装在瓶子中。
NO1:定义接口,提供方法获取此功能需要的属性,食品名称、价钱’包装方式
NO2:实现NO1接口,2个抽象类汉堡和饮料
NO4:定义包装方式接口。
NO3:实现NO4接口,2个实现类塑料袋包装和瓶子包装,提供给NO2使用
NO5:继承NO2接口,4个对象分别蔬菜汉堡、鸡肉汉堡、可乐、冷饮
NO6:输出NO1接口中的属性
NO7:构建套餐,蔬菜套餐,非蔬菜套餐
用户通过NO7获取到套餐,通过NO6输出套餐内容
优点: 1、建造者独立,易扩展。 2、便于控制细节风险。
缺点: 1、产品必须有共同点,范围有限制。 2、如内部变化复杂,会有很多的建造类。
使用场景: 1、需要生成的对象具有复杂的内部结构。 2、需要生成的对象内部属性本身相互依赖。
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder;
public interface Item {
public String name();
public Packing packing();
public float price();
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder;
public interface Packing {
public String pack();
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.core;
import java.util.ArrayList;
import java.util.List;
import com.pattern.builder.Item;
public class Meal {
private List- items = new ArrayList
- ();
public void addItem(Item item) {
items.add(item);
}
public float getCost() {
float cost = 0.0f;
for (Item item : items) {
cost += item.price();
}
return cost;
}
public void showItems() {
for (Item item : items) {
System.out.print("Item : " + item.name());
System.out.print(", Packing : " + item.packing().pack());
System.out.println(", Price : " + item.price());
}
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.core;
import com.pattern.builder.impl.ChickenBurger;
import com.pattern.builder.impl.Coke;
import com.pattern.builder.impl.Pepsi;
import com.pattern.builder.impl.VegBurger;
public class MealBuilder {
public Meal prepareVegMeal() {
Meal meal = new Meal();
meal.addItem(new VegBurger());
meal.addItem(new Coke());
return meal;
}
public Meal prepareNonVegMeal() {
Meal meal = new Meal();
meal.addItem(new ChickenBurger());
meal.addItem(new Pepsi());
return meal;
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.impl;
import com.pattern.builder.item.impl.Burger;
public class ChickenBurger extends Burger {
@Override
public float price() {
return 50.5f;
}
@Override
public String name() {
return "Chicken Burger";
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.impl;
import com.pattern.builder.item.impl.ColdDrink;
public class Coke extends ColdDrink {
@Override
public float price() {
return 30.0f;
}
@Override
public String name() {
return "Coke";
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.impl;
import com.pattern.builder.item.impl.ColdDrink;
public class Pepsi extends ColdDrink {
@Override
public float price() {
return 35.0f;
}
@Override
public String name() {
return "Pepsi";
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.impl;
import com.pattern.builder.item.impl.Burger;
public class VegBurger extends Burger {
@Override
public float price() {
return 25.0f;
}
@Override
public String name() {
return "Veg Burger";
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.item.impl;
import com.pattern.builder.Item;
import com.pattern.builder.Packing;
import com.pattern.builder.packing.impl.Wrapper;
public abstract class Burger implements Item {
@Override
public Packing packing() {
return new Wrapper();
}
@Override
public abstract float price();
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.item.impl;
import com.pattern.builder.Item;
import com.pattern.builder.Packing;
import com.pattern.builder.packing.impl.Bottle;
public abstract class ColdDrink implements Item {
@Override
public Packing packing() {
return new Bottle();
}
@Override
public abstract float price();
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.packing.impl;
import com.pattern.builder.Packing;
public class Bottle implements Packing {
@Override
public String pack() {
return "Bottle";
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.packing.impl;
import com.pattern.builder.Packing;
public class Wrapper implements Packing {
@Override
public String pack() {
return "Wrapper";
}
}
/*
*Copyright (c) 2016, gp.inc and/or its affiliates. All rights reserved.
*/
package com.pattern.builder.test;
import com.pattern.builder.core.Meal;
import com.pattern.builder.core.MealBuilder;
public class BuilderPatternDemo {
public static void main(String[] args) {
MealBuilder mealBuilder = new MealBuilder();
Meal vegMeal = mealBuilder.prepareVegMeal();
System.out.println("Veg Meal");
vegMeal.showItems();
System.out.println("Total Cost: " + vegMeal.getCost());
Meal nonVegMeal = mealBuilder.prepareNonVegMeal();
System.out.println("\n\nNon-Veg Meal");
nonVegMeal.showItems();
System.out.println("Total Cost: " + nonVegMeal.getCost());
}
}
运行结果
Veg Meal
Item : Veg Burger, Packing : Wrapper, Price : 25.0
Item : Coke, Packing : Bottle, Price : 30.0
Total Cost: 55.0
Non-Veg Meal
Item : Chicken Burger, Packing : Wrapper, Price : 50.5
Item : Pepsi, Packing : Bottle, Price : 35.0
Total Cost: 85.5