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();
    }
}

 

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