代码详解设计模式--建造者模式

小鱼儿 2022-03-15 07:12 81阅读 0赞

# 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。

*  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。

![UML][]

// 点单
    public interface Item { 
       public String name();
       public Packing packing();
       public float price();    
    }
    
    // 打包
    public interface Packing { 
       public String pack();
    }
    
    // 包装纸
    public class Wrapper implements Packing { 
       @Override
       public String pack() { 
          return "Wrapper";
       }
    }
    
    // 瓶子
    public class Bottle implements Packing { 
       @Override
       public String pack() { 
          return "Bottle";
       }
    }
    
    // 汉堡
    public abstract class Burger implements Item { 
       @Override
       public Packing packing() { 
          return new Wrapper();
       }
     
       @Override
       public abstract float price();
    }
    
    // 冷饮
    public abstract class ColdDrink implements Item { 
        @Override
        public Packing packing() { 
           return new Bottle();
        }
     
        @Override
        public abstract float price();
    }
    
    // 素食汉堡
    public class VegBurger extends Burger { 
       @Override
       public float price() { 
          return 25.0f;
       }
     
       @Override
       public String name() { 
          return "Veg Burger";
       }
    }
    
    // 鸡肉汉堡
    public class ChickenBurger extends Burger { 
       @Override
       public float price() { 
          return 50.5f;
       }
     
       @Override
       public String name() { 
          return "Chicken Burger";
       }
    }
    
    // 可口可乐
    public class Coke extends ColdDrink { 
       @Override
       public float price() { 
          return 30.0f;
       }
     
       @Override
       public String name() { 
          return "Coke";
       }
    }
    
    // 百事可乐
    public class Pepsi extends ColdDrink { 
       @Override
       public float price() { 
          return 35.0f;
       }
     
       @Override
       public String name() { 
          return "Pepsi";
       }
    }
    
    // 快餐
    public class Meal { 
       private List<Item> items = new ArrayList<Item>();    
        
       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());
          }        
       }    
    }
    
    // 快餐建造者
    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;
       }
    }
    
    // 使用示例
    public class Demo { 
       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("Non-Veg Meal");
          nonVegMeal.showItems();
          System.out.println("Total Cost: " +nonVegMeal.getCost());
       }
    }

[UML]: /images/20220315/ea46336f80ec44e1aaacf415f654f229.png