链式编程:遇到多个构造器参数(Constructor Parameters)时要考虑用构建器(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;

     // 构造器，静态内部类
     public static class Builder {
         // 必要参数
         private final int servingSize;
         private final int servings;
         // 可选参数
         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;//返回Builder类对象本身，以便把调用链接起来
         }

         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;
     }

     @Override
     public String toString() {
         return "[" +
                 "servingSize:" + servingSize +
                 ",servings:" + servings +
                 ",calories:" + calories +
                 ",fat:" + fat +
                 ",sodium:" + sodium +
                 ",carbohydrate:" + carbohydrate +
                 "]";
     }

     public static void main(String[] args) {
         NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8)
                 .calories(100).sodium(35).carbohydrate(27).build();

         System.out.println(cocaCola);
     }
 }

构造Map

 package com.jt.mongo.demo.basic.util;

 import java.util.HashMap;
 import java.util.Map;

 /**
  * 构建拥有多个值的Map(简化map操作):<br/>
  * map = ParamBuilder.of().withParam().withParam().withParam().build();.
  *
  * @author weihainan.
  * @since 0.1 created on 2017/2/8.
  */
 public final class ParamBuilder {

     private Map<String, Object> paramMap = new HashMap<>(6);

     private ParamBuilder() {
         // empty
     }

     /**
      * 获取ParamBuilder对象.
      */
     public static ParamBuilder of(){
         return new ParamBuilder();
     }

     /**
      * 获取ParamBuilder对象并设置一对key-value.
      */
     public static ParamBuilder of(String paramName, Object paramValue) {
         return new ParamBuilder().withParam(paramName, paramValue);
     }

     /**
      * 设置参数，可多次操作.
      */
     public ParamBuilder withParam(String paramName, Object paramValue) {
         paramMap.put(paramName, paramValue);
         return this;
     }

     /**
      * 获取最终的map.
      */
     public Map<String, Object> build() {
         return paramMap;
     }
 }