Java建造者模式

参考：https://www.yiibai.com/design_pattern/builder_pattern.html

使用简单的对象逐步构建复杂的对象

1. 创建一个商品接口：有商品名称，打包方式，价格。

package Test0627;

public interface Item {
    public String name();
    public Packing packing();
    public float price();
}

2. 创建打包类，是个接口，提供打包方式方法

package Test0627;

public interface Packing {
    public String pack();
}

3. 实现打包接口

瓶装

package Test0627;

public class Bottle implements Packing {
    @Override
    public String pack() {
        return "bottle...";
    }
}

包装

package Test0627;

public class Wrapper implements Packing {

    @Override
    public String pack() {
        return "wrapper...";
    }
}

3. 创建一个冰饮类（抽象类）实现商品接口，
   重写打包方法，返回瓶装对象
   将price（）设为抽象方法

package Test0627;

public abstract class ColdDrink implements Item {
    @Override
    public Packing packing() {
        return new Bottle();
    }

    @Override
    public abstract float price();
}

4. 创建一个汉堡类（抽象类）实现商品接口，
   重写打包方法，返回包装对象，
   将price（）设为抽象方法

package Test0627;

public abstract class Burger implements Item{
    @Override
    public Packing packing(){
        return new Wrapper();
    }

    @Override
    public abstract float price();
}

5. 创建蔬菜汉堡类，继承汉堡类，重写item里的name和price

package Test0627;

public class VegBurger extends Burger {
    @Override
    public String name() {
        return "veg burger";
    }

    @Override
    public float price() {
        return 25.0f;
    }
}

6. 创建鸡肉汉堡类，继承汉堡类，重写item里的name和price

package Test0627;

public class ChickenBurger extends Burger {
    @Override
    public String name() {
        return "chicken burger";
    }

    @Override
    public float price() {
        return 50.0f;
    }
}

7. 创建可乐类，继承冰饮，重写item里的name和price

package Test0627;

public class Coke extends ColdDrink {
    @Override
    public String name() {
        return "coke";
    }

    @Override
    public float price() {
        return 12.0f;
    }
}

8. 创建百事类，继承冰饮，重写item里的name和price

package Test0627;

public class Pepsi extends ColdDrink {
    @Override
    public String name() {
        return "pepsi";
    }

    @Override
    public float price() {
        return 15.0f;
    }
}

9.完成了商品的信息，接下来要创建点餐类

package Test0627;

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

public class Meal {
    //定义一个集合，存储item信息
    private List iterms = new ArrayList();

    //定义一个方法，往list集合里添加item信息
    public void addItem(Item iterm){
        iterms.add(iterm);
    }

    //定义一个方法，通过循环计算出list和里item的总价
    public float getCost(){
        float cost = 0.0f;

        for(Item iterm : iterms){
            cost += iterm.price();
        }
        return cost;
    }
    
    //定义一个方法，输出list每个item的信息
    public void showItems(){
        for(Item iterm:iterms){
            System.out.print("Item: "+iterm.name());
            System.out.print(", Packing: "+iterm.packing().pack());
            System.out.println(", Price: "+ iterm.price());
        }
    }
}

10. 创建组合餐类

package Test0627;

public class MealBuilder {
    //蔬菜餐
    public Meal prepareVegMeal(){
        Meal meal = new Meal();
        //添加蔬菜汉堡和可乐
        meal.addItem(new VegBurger());
        meal.addItem(new Coke());
        return meal;
    }

    //鸡肉餐
    public Meal prepareNonVegMeal(){
        Meal meal = new Meal();
        //添加鸡肉汉堡和百事
        meal.addItem(new ChickenBurger());
        meal.addItem(new Pepsi());
        return meal;
    }
}

11. 测试一下

package Test0627;

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());
    }
}