多参数[构建器]

 在多参数（一般在大于4个参数以上）的情况下 或者参数个数不清楚的情况下使用。

 

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{  
        private final int servingSize;  
        private final int servings;  
          
        private int calories = 0;  
        private int fat = 0;  
        private int sodium = 0;  
        private int carbohydrate = 0;  
          
        public Builder(int servingSize, int servings) {  
            super();  
            this.servingSize = servingSize;  
            this.servings = servings;  
        }  
          
        public Builder calories(int val){  
            this.calories=val;  
            return this;  
        }  
          
        public Builder fat(int val){  
            this.fat=val;  
            return this;  
        }  
          
        public Builder sodium(int val){  
            this.sodium=val;  
            return this;  
        }  
          
        public Builder carbohydrate(int val){  
            this.carbohydrate=val;  
            return this;  
        }  
          
        public NutritionFacts build(){  
            return new NutritionFacts(this);  
        }  
    }  
      
    private NutritionFacts(Builder builder){  
        this.servingSize=builder.servingSize;  
        this.servings=builder.servings;  
        this.calories=builder.calories;  
        this.fat=builder.fat;  
        this.sodium=builder.sodium;  
        this.carbohydrate=builder.carbohydrate;  
    }  
      
}  

调用：

 

NutritionFacts mNutritionFacts=new NutritionFacts.Builder(240, 8). 
                        calories(100).carbohydrate(27).sodium(35).build();