【JAVA】Builder模式_java builder模式面试题-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_27020369/article/details/78631210

本文介绍了一个使用Java实现的Builder模式案例，通过一个营养成分表的例子展示了如何利用Builder模式来构造复杂的对象实例，此模式适用于拥有多个可选参数的情况。

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package com.wangyao.utils;


public class NutritionFacts {
	private final int servingSize;
	private final int servings;
	private final int calories;
	private final int fat;
	private final int carbohydrate;
	private final int sodium;
	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;
		carbohydrate = builder.carbohydrate;
		sodium = builder.sodium;
	}
	
	public static void main(String[] args){
		NutritionFacts cocaCola = new NutritionFacts.Builder(210, 10).calories(10).sodium(35).calories(27).build();
	}
	
}

使用场景：多于4个变量。比JAVA BEAN模式线程安全，比重叠式构造清晰、