Java 设计模式 — 建造者模式(4)

梦里梦外; 2024-04-03 09:04 57阅读 0赞

## 一、浅谈建造者模式 ##

**建造者模式会将多个简单的对象一步步构建成一个复杂的对象。**显然，这种设计模式也属于创建型模式。这种模式同样也提供了创建对象的最佳方式。**xxxBuilder 类会一步步去构造最终我们所需的对象，但是 xxxBuilder 类独立于其它的对象。**

**建造者模式有点像高中我们数学所学的排列组合，它将不同种类的产品相互组合，得到很多种排列方式。就好比我们日常生活中，在餐馆点餐，餐馆会向我们推荐单人餐、四人餐、六人餐等等之类的套餐，不同种类的菜品排列组合成了套餐。在建造者模式中，我们也可以将其形象的理解为"套餐"。**

"套餐" 在建造者模式如何体现呢？下面我们看代码来一起理解~

## **二、测试代码** ##

### **1）代码架构图** ###

![12109fd9c5cd47d89ae54139e1757599.png][]

###  **2）代码包图** ###

![6dd35752acaa4450ae01083add8e5324.png][]

###  **3）代码** ###

#### **Interface** ####

**<1> PackageFood**

public interface PackageFood {
        String packageFood();
    }

**<2> Food**

public interface Food {
        String foodName();
        double foodPrice();
        PackageFood packageInstance();
    }

#### ImplPackage ####

**<1> Cup**

public class Cup implements PackageFood {
        @Override
        public String packageFood() {
            return "Use a cup to package.";
        }
    }

**<2> Plate**

public class Plate implements PackageFood {
        @Override
        public String packageFood() {
            return "Use a plate to package.";
        }
    }

#### AbstractClass ####

**<1> Dishes**

public abstract class Dishes implements Food {
        @Override
        public PackageFood packageInstance() {
            return new Plate();
        }
    }

**<2> Drinks**

public abstract class Drinks implements Food {
        @Override
        public PackageFood packageInstance() {
            return new Cup();
        }
    }

#### Bean ####

#### 1）DishesBean ####

**<1> Mapo Tofu**

public class MapoTofu extends Dishes {
        @Override
        public String foodName() {
            return "Mapo Tofu";
        }
    
        @Override
        public double foodPrice() {
            return 16.32D;
        }
    }

**<2> Rice**

public class Rice extends Dishes {
        @Override
        public String foodName() {
            return "Rice";
        }
    
        @Override
        public double foodPrice() {
            return 1.00D;
        }
    }

**<3> ZongZi**

public class ZongZi extends Dishes {
        @Override
        public String foodName() {
            return "ZongZi";
        }
    
        @Override
        public double foodPrice() {
            return 8.78D;
        }
    }

#### 2）DrinksBean ####

**<1> FruitTea**

public class FruitTea extends Drinks {
        @Override
        public String foodName() {
            return "Fruit Tea";
        }
    
        @Override
        public double foodPrice() {
            return 18.20D;
        }
    }

**<2> HuiYuanJuice**

public class HuiYuanJuice extends Drinks {
        @Override
        public String foodName() {
            return "HuiYuan Juice";
        }
    
        @Override
        public double foodPrice() {
            return 10.00D;
        }
    }

#### Meal ####

public class Meal {
        private final ArrayList<Food> foods = new ArrayList<>();
    
        public void addFood(Food food) {
            foods.add(food);
        }
    
        public void totalPrice() {
            double cost = 0.0D;
            for (Food food : foods) {
                cost += food.foodPrice();
            }
            System.out.println("总费用为: " + cost);
        }
    
        public void whatFood() {
            for (Food food : foods) {
                System.out.println(food.foodName() + " "
                        + food.foodPrice() + " "
                        + food.packageInstance().packageFood());
            }
        }
    }

#### MealBuilder ####

public class MealBuilder {
    
        /**
         * 套餐一
         * prepareFirstSetOfDish
         * @return Meal
         */
        public Meal prepareFirstSetOfDish() {
            Meal meal = new Meal();
            meal.addFood(new MapoTofu());
            meal.addFood(new Rice());
            meal.addFood(new HuiYuanJuice());
            return meal;
        }
    
        /**
         * 套餐二
         * prepareFirstSetOfDish
         * @return Meal
         */
        public Meal prepareSecondSetOfDish() {
            Meal meal = new Meal();
            meal.addFood(new MapoTofu());
            meal.addFood(new ZongZi());
            meal.addFood(new FruitTea());
            return meal;
        }
    
        /**
         * 四人餐
         * prepareFourPersonDish
         * @return Meal
         */
        public Meal prepareFourPersonDish () {
            Meal meal = new Meal();
            meal.addFood(new MapoTofu());
            meal.addFood(new ZongZi());
            meal.addFood(new Rice());
            meal.addFood(new FruitTea());
            meal.addFood(new HuiYuanJuice());
            return meal;
        }
    }

#### Test 测试类 ####

public class Test {
        public static void main(String[] args) {
            MealBuilder mealBuilder = new MealBuilder();
    
            // 套餐一
            System.out.println("套餐一");
            Meal mealFirst = mealBuilder.prepareFirstSetOfDish();
            mealFirst.whatFood();
            mealFirst.totalPrice();
    
            System.out.println();
    
            // 套餐二
            System.out.println("套餐二");
            Meal mealSecond = mealBuilder.prepareSecondSetOfDish();
            mealSecond.whatFood();
            mealSecond.totalPrice();
    
            System.out.println();
    
            // 四人餐
            System.out.println("四人餐");
            Meal fourPersonMeal = mealBuilder.prepareFourPersonDish();
            fourPersonMeal.whatFood();
            fourPersonMeal.totalPrice();
        }
    }

**测试结果**

套餐一
    Mapo Tofu 16.32 Use a plate to package.
    Rice 1.0 Use a plate to package.
    HuiYuan Juice 10.0 Use a cup to package.
    总费用为: 27.32
    
    套餐二
    Mapo Tofu 16.32 Use a plate to package.
    ZongZi 8.78 Use a plate to package.
    Fruit Tea 18.2 Use a cup to package.
    总费用为: 43.3
    
    四人餐
    Mapo Tofu 16.32 Use a plate to package.
    ZongZi 8.78 Use a plate to package.
    Rice 1.0 Use a plate to package.
    Fruit Tea 18.2 Use a cup to package.
    HuiYuan Juice 10.0 Use a cup to package.
    总费用为: 54.3

#### 总结： ####

**建造者模式是将不同的简单类经过一系列操作，最终构建为一个复杂对象的过程。建造者模式更关注的时零件装配的过程。建造者模式通常使用在一些基础组件不改变，但是组合经常会发生变化的时候。**

[12109fd9c5cd47d89ae54139e1757599.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/98596aaf8dc94586aa766029e4579da4.png
[6dd35752acaa4450ae01083add8e5324.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/c52e6073ac29446f91804ded19c5b3f7.png