Effective Java Second Edition --- Builder Pattern

    如果类的构造器或者静态工厂中有多个参数，设计这种类时，Builder模式是一种不错的选择，特别是当大多数参数是可选的时候。

与使用传统的重载构造函数模式相比，使用Builder模式的客户端代码更易于阅读和编写，构造器也比javabeens更加安全。

代码如下：

/**
 * Created by zhanga.fnst on 2016/3/14.
 */
public class NutritionFacts {
    private final int servingSize;
    private final int servings;
    private final int calories;
    private final int flat;
    private final int sodium;
    private final int carbohydrate;

    public  static class Builder{
        //required parameters
        private final int servingSize;
        private final int servings;

        //Optional parameters
        private  int calories = 0;
        private  int flat = 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 flat(int val){
            flat = 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;
        flat = builder.flat;
        sodium = builder.sodium;
        carbohydrate = builder.carbohydrate;
    }
}

main方法：

/**
 * Created by zhanga.fnst on 2016/3/14.
 */
public class TestMain {
    NutritionFacts cocaCola = new NutritionFacts.Builder(240,8).
            calories(100).sodium(35).carbohydrate(27).build();
}