构造器模板

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package org.effectivejava.examples.chapter02.item02.builder;   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 {         // Required parameters         private final int servingSize;         private final int servings;           // Optional parameters - initialized to default values         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;         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();     } }