《effective java》-设计模式-构造器模式

最新推荐文章于 2022-07-11 11:54:31 发布

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#设计模式

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这篇博客探讨了在Java中如何通过Builder模式解决构造器和静态工厂方法在处理多个可选参数时的局限性。作者展示了如何创建一个`No2Builder`类，并利用Builder模式来构建对象，允许更灵活的参数配置。在示例中，`No2Builder`的实例可以通过链式调用来设置不同的属性值，提高了代码的可读性和可维护性。

最近在研读《effective java》这本书，做一个简单的笔记。

构造器和静态工厂有一个共同的局限性，都不能很好的扩展大量的可选参数，考虑到很多可选参数的构造，我们引入一个新的设计模式。即构造器模式。

package EffectiveJava;

/**
 * @author 韦海涛
 * @version 1.0
 * @date 3/30/2021 11:23 PM
 */


//Builder Pattern
public class No2Builder {
    private final int servingSize;
    private final int serving;
    private final int calories;
    private final int fat;
    private final int sodium;
    private final int carbohydrate;


    private static class Builder {
        private final int servingSize;
        private final int serving;
        private int calories = 0;
        private int fat = 0;
        private int sodium = 0;
        private int carbohydrate = 0;

        public Builder(int servingSize, int serving) {
            this.servingSize = servingSize;
            this.serving = serving;
        }
        public Builder calories(int val){
            calories = val;
            return this;
        }
        public Builder fat(int val){
            fat = val;
            return this;
        }
        public Builder sodium(int val){
            sodium = val;
            return this;
        }
        public Builder carbohydrate(int val){
            carbohydrate = val;
            return this;
        }
        public No2Builder builder(){
            return new No2Builder(this);
        }
    }
    private No2Builder(Builder builder){
        servingSize = builder.servingSize;
        serving = builder.serving;
        calories = builder.calories;
        fat = builder.fat;
        sodium = builder.sodium;
        carbohydrate = builder.carbohydrate;
    }

    public int getCalories() {
        return calories;
    }

    public static void main(String[] args) {
        No2Builder no2Builder = new Builder(240,9).calories(100).fat(10).sodium(1).builder();
        System.out.println(no2Builder.getCalories());
    }

}