item 2 leekyunghee - JAVA-JIKIMI/EFFECTIVE-JAVA3 GitHub Wiki

public class NutritionFacts {
    private final int servingSize; // (ml/1회 제공량) 필수 
    private final int servings;    // (회/총 n회 제공량) 필수
    private final int calories;    // (1회 제공량당)   선택
    private final int fat;         // (g/1회 제공량)   선택
    private final int sodium;      // (mg/1회 제공량)  선택
    private final int carbohydrate;  // (g/1회 제공량) 선택
    
    public NutritionFacts(int servingSize, int servings) {
        this(servingSize, servings, 0);
    }
    
    public NutritionFacts(int servingSize, int servings, int calories) {
        this(servingSize, servings, calories, 0);
    }

    public NutritionFacts(int servingSize, int servings, int calories, int fat) {
        this(servingSize, servings, calories, fat, 0);
    }

    public NutritionFacts(int servingSize, int servings, int calories, int fat, int sodium) {
        this(servingSize, servings, calories, fat, sodium, 0);
    }
    
    public NutritionFacts(int servingSize, int servings, int calories, int fat, int sodium, int carbohydrate) {
         this.servingSize = servingSize;
         this.servings = servings;
         this.calories = calories;         
         this.fat = fat;
         this.sodium = sodium;
         this.carbohydrate = carbohydrate;
    }
}

NutritionFacts cocaCola = new NutritionFacts(240, 8,  100, 0, 35,  27);

NutritionFacts cocaCola = new NutritionFacts();
cocaChola.setServingSize(240);
cocaCola.setServings(8);
cocaCola.setCalories(100);
cocaCola.setSodium(35);
cocaCola.setCarbohydrate(27);

public class NutritionFacts {
   private final int servingSize;
   private final int servings;
   private final int calories;
   private final int fat;
   private final int sodium;
   private final int carbohydrate;

   public static class Builder {
       // 필수 매개변수 
       private final int servingSize;
       private final int servings;
      
       // 선택 매개변수 - 기본값으로 초기화 한다. 
       private int calories = 0;
       private int fat = 0;
       private int sodium = 0;
       private int carbohydrate = 0;

       public Builder(int servingSize, int servings) {
           this.servingSize = servingSize;
           this.servings = servings;
       }
       
       public Builder calories(int val) {
           calories = val;
           return this;
       } 
       public Builder fat(int val) {
           fat = val;
           return this;
       } 
       public Builder sodium(int val) {
           sodium = val;
           return this;
       } 

       public Builder carbohydrate(int val) {
           carbohydrate = val;
           return this;
       }
       
       public NutritionFacts(Builder builder) {
            servingSize = builder.servingSize;
            servings    = builder.servings;
            calories    = builder.calories;
            fat         = builder.fat;
            sodium      = builder.sodium;
            carbohydrate = builder.carbohydrate;

       }


   }

}


}

// 실제 위의 클래스를 사용하는 클라이언트 코드
NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8).calories(100).sodium(35).carbohydrate(27).build();

// 계층적으로 설계된 클래스와 잘 어울리는 빌더 패턴
public abstract class Pizza {
    public enum Topping { HAM, MUSHROOM, ONION, PEPPER, SAUSAGE } 
    final Set<Topping> toppings;
    
    abstract static class Builder<T extends Builder<T>> {
        EnumSet<Topping> toppings = EnumSet.noneOf(Topping.class);
        public T addTopping(Topping topping) { 
                addToppings.add(Objects.requireNonNULL(topping));
                return self();
        }   
        // 하위  클래스는 이 메서드를 재정의 하여 "this"를 반환하도록 해야한다.  
        abstract Pizza build();
        protected abstract T self();
    }
    Pizza(Builder<?> builder) {
        toppings = builder.toppings.clone();   // Item 50참조  
    } 
}