对象的创建

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 carbohydrate = 0;
			   private int sodium = 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 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;
			   carbohydrate = builder.carbohydrate;
			   sodium = builder.sodium;
		   }
	}