//构建器抽象类，为不同类的实现提供

public interface Builder<T> {

    public T build();

}

/**

 * @描述: 营养表

 */

public class NutritionFacts {

    private final int servingSize;// required

    private final int servings;// required

    private final int calories;// optional

    private final int fat;// optional

    private final int sodium;// optional

    private final int carbohydrate;// optional

    public static class Builder1 implements Builder<NutritionFacts>{

        private final int servingSize;// required 食用分量

        private final int servings;// required （食品等的）一份

        private int calories;// optional 卡路里

        private int fat;// optional

        private int sodium;// optional 钠

        private int carbohydrate;// optional 碳水化合物；糖类

        public Builder1(int servingSize,int servings){

            this.servingSize = servingSize;

            this.servings = servings;

        }

        public Builder1 calories(int calories) {

            this.calories = calories;

            return this;

        }

        public Builder1 fat(int fat) {

            this.fat = fat;

            return this;

        }

        public Builder1 sodium(int sodium) {

            this.sodium = sodium;

            return this;

        }

        public Builder1 carbohydrate(int carbohydrate) {

            this.carbohydrate = carbohydrate;

            return this;

        }

        @Override

        public NutritionFacts build() {

            return new NutritionFacts(this);

        }

    }

    private NutritionFacts(Builder1 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;

    }

    public static void main(String[] args) {

        NutritionFacts cocacola = new NutritionFacts.Builder1(, ).calories().sodium().carbohydrate().build();

    }

}

为非必须参数设置值，返回Build自身可以把调用链接起来

好处：

、可以用单个builder创建多个对象，builder的参数可以在创建对象期间调整，可以随着对象不同而改变。builder可以自动填充某些域，例如每次创建对象时自动增加序号。

、这是一个很好的抽象工厂（abstract factory）。客户端只要将这样一个builder传给方法，该方法能为客户端创建一个或多个对象。

一个通用类型的bulider

public interface Builder<T>{

  public T build();

}