Builder Design Pattern

最新推荐文章于 2023-04-11 16:03:37 发布

转载最新推荐文章于 2023-04-11 16:03:37 发布 · 146 阅读

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原文链接：http://www.cnblogs.com/codingyangmao/p/11271904.html

本文深入解析建造者模式，一种创建型设计模式，通过逐步构建复杂对象来简化创建过程。通过实例展示如何使用Java实现该模式，包括定义食物项接口、包装接口及其实现类，抽象基类提供默认功能，具体类实现复杂对象构建，最后通过Meal类和MealBuilder类演示模式应用。

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Builder pattern builds a complex object using simple objects and using a step by step approach.

This type of design pattern comes under creational pattern.

Below is an example of Buider Pattern using Diagram and Code example.

Code that matches with above diagram.

Step 1. Create an Interface representing food item and package

Item.java

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

Packing.java

public interface Packing{
     public String pack();
}

Step 2. Create Concrete classes implementing the Packing interface.

Wrapper.java

public class Wrapper implements Packing{
   @Override
   public String pack(){
     return (""Wrapper");
   }
}

Bottle.java

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

Step 3 Create abstract classes implementing the item interface providing default functionalities.

Burger.java

public abstract class Burger implements Item {

   @Override
   public Packing packing() {
      return new Wrapper();
   }

   @Override
   public abstract float price();
}

ColdDrink.java

public abstract class ColdDrink implements Item {

    @Override
    public Packing packing() {
       return new Bottle();
    }

    @Override
    public abstract float price();
}

Step 4 Create concrete classes extending Burger and ColdDrink classes

VegBurger.java

public class VegBurger extends Burger {

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

   @Override
   public String name() {
      return "Veg Burger";
   }
}

ChickenBurger.java

public class ChickenBurger extends Burger {

   @Override
   public float price() {
      return 50.5f;
   }

   @Override
   public String name() {
      return "Chicken Burger";
   }
}

Coke.java

public class Coke extends ColdDrink {

   @Override
   public float price() {
      return 30.0f;
   }

   @Override
   public String name() {
      return "Coke";
   }
}

Pepsi.java

public class Pepsi extends ColdDrink {

   @Override
   public float price() {
      return 35.0f;
   }

   @Override
   public String name() {
      return "Pepsi";
   }
}

Step 5. Create a Meal class having Item objects defined above.

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

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());
      }        
   }    
}

Step 6. Create a MealBuilder class, the actual builder class responsible to create Meal objects.

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;
   }
}

Step 7. Build the Demo class.

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());
   }
}

转载于:https://www.cnblogs.com/codingyangmao/p/11271904.html