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;
    }
}