Builder模式

来源：互联网发布：淘宝怎么打新品标编辑：程序博客网时间：2024/04/30 04:24

Builder模式其中的一个作用是在创建类的构造器的时候，把可选的和必须的参数分离。下面是一个例子：

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 {        //对象的必选参数        private final int servingSize;        private final int servings;        //对象的可选参数的缺省值初始化        private int calories = 0;        private int fat = 0;        private int carbohydrate = 0;        private int sodium = 0;        //只用少数的必选参数作为构造器的函数参数        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 carbohydrate(int val) {            carbohydrate = val;            return this;        }        public Builder sodium(int val) {            sodium = val;            return this;        }        public NutritionFacts build() {            return new NutritionFacts(this);        }    }    private NutritionFacts(Builder builder) {        servingSize = builder.servingSize;        servings = builder.servings;        calories = builder.calories;        fat = builder.fat;        sodium = builder.sodium;        carbohydrate = builder.carbohydrate;    }

    public static void main(String[] args) {        NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8).calories(100)            .sodium(35).carbohydrate(27).build();                NutritionFacts cc = new NutritionFacts.Builder(30, 34).build();    }

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可以通过Builer方式，只写一个构造方法。

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